THE NEW ZEALAND OFFICIAL YEAR-BOOK, 1925

It has been acknowledged by the leading hydrologists in Europe that New Zealand possesses the most valuable mineral waters in existence. Not only are these mineral waters interesting from a tourist's point of view, but they are, because of their medicinal value, of great therapeutic importance, and, as a Dominion asset, worthy of the deepest scientific consideration.

From the spectacular aspect only a brief mention need be made in this article, as a full description of springs, geysers, and mud-pools has been given in Dr. Herbert's book, "The Hot Springs of New Zealand"—a book that presents a comprehensive and vivid picture of the main manifestations of thermal activity in New Zealand.

Dealing with the medical-scientific aspect of the mineral waters, the space of this article will permit only the shortest account of the treatments; and, as the Rotorua Spa is of premier importance, the article will be confined almost entirely to its operations.

Since and as the result of experience gained during the war the subject of hydrotherapy has been recreated on modern scientific lines, and the actions of thermal mineral waters have been investigated, both chemically and physiologically, in determining their therapeutic value in the treatment of disease.

The mineral waters which have been harnessed for therapeutic use at the Rotorua Spa are of two main varieties—viz., the "Rachel," which is an alkaline, sulphuretted water, emollient to the skin, and sedative in reaction; and the "Priest," or free-acid water, which, due to the presence of free sulphuric acid, is mainly stimulating and tonic in reaction. There is, in addition to the foregoing, a valuable silicious mud similar to that found in Pistany, in Czecho-Slovakia, which, in its own sphere in hydrotherapy, exerts its influence as a curative agent.

However, it is in the "Priest" waters that one finds one's most valuable ally in the treatment of arthritis, fibrositis (the so-called rheumatic affections), and cases of nervous debility. The "Rachel" and mud baths are used mostly in those cases of fibrositis where the condition requires a softening effect; and in the types where pain is a manifest symptom these baths are invaluable as soothing and sedative agents.

In these natural acid baths the reactions are mainly stimulating, with increased hyperaemia in the parts submerged, and marked lessening of pain and swelling in the affected joints and tissues. Those waters containing free carbonic-acid gas are used for the cases of fibrositis in which the circulation requires the stimulating action of gaseous baths.

The "New Priest" waters, containing approximately 16-80 grains per gallon of free sulphuric acid, are utilized in the form of open pools, deep step-down baths, and slipper baths. They are prescribed at a suitable temperature for the individual case.

The "Old Priest" waters, containing a much lower degree of free acid (3.77 grains to the gallon), and of varying temperatures (from 84° F. to 102° F.), are used for treatment at their source. The waters, percolating through their pumice - bed, are confined in pools, and contain free carbonic-acid gas, bubbling through the water.

The very strong "Postmaster" waters are also confined within pools on the natural pumice - bed, and, by a primitive arrangement of wooden sluice-valves, maintained at three ranges of temperature—viz., 104°, 106°, and 108° F. They contain 22.29 grains of free sulphuric acid to the gallon, and are strongly counter-irritant in their reactions.

In such a brief account as this one can only deal in generalizations, and the forms of treatment mentioned must necessarily be subject to wide variations. In any form of hydro-therapeutic treatment the regime must be adapted to the individual manifestations of the disease, and no routine rules or regulations can be laid down in spa operations.

The "New Priest" waters are, for the most part, prescribed for patients suffering from subacute or chronic fibrositis, subacute or chronic gout, and the various forms of arthritis. Except in cases of marked debility, those patients are given graduated baths, at temperatures ranging from 102° to 104° F., from ten to fifteen minutes daily. Most of the baths are fitted with a subaqueous douche having a pressure of 25 lb., which is directed under water on the affected tissues. The bath is usually followed by a light or hot pack, according to the needs of the case.

The subthermal "Old Priest" waters (temperature 84° F.), containing a high degree of free carbonic-acid gas, are particularly valuable in the treatment of functional nervous disease, and the methods of administration are similar to those obtaining at Nauheim. The reactions are markedly stimulating through the sympathetic nervous system, and bring about, by reflex action, a tonic effect on the heart.

The "Postmaster" baths are used in the treatment of the more chronic forms of fibrositis, arthritis deformans, and gout, requiring a more or less heroic type of procedure. They are usually prescribed in combination—i.e., a certain time in each pool, commencing with the lowest temperature. The hyperœmic reaction is most marked, and in many of the cases where pain is a predominant symptom there is a temporary paralysis of the surface nerves, as well as a strong reflex excitation of the heart. For this reason these baths are not given to patients suffering from cardiac weakness.

The treatment of gout depends entirely on the individual manifestations. In certain subacute and chronic types fairly high temperatures (104° to 106° F., with hot packs) of "Priest" water are employed, in order to hasten the absorption of exudates and the elimination of uric acid. In acute cases of acute gout more sedative measures are pursued, such as "Rachel" baths at neutral temperatures, local mud packs, and rest. As soon as the conditions permit, these patients are changed over to acid water baths. Cases of chronic gout exhibiting metabolic stagnation sometimes receive considerable benefit from the counter-irritant effects of the strongly acid "Postmaster" waters.

Separate establishments, containing the most modern apparatus of sprays, douches, hot steam, &c., are available for wet massage and treatments of the Aix-Vichy type.

The massage-rooms are fitted with the latest installations of electrical equipment—Bristowe tables, diathermy, high frequency, Bergonie chair, X-ray, Schnée baths, Greville hot air, and other apparatus for carrying out the most up-to-date methods of electrical-therapeutic treatments.

The baths are administered by a trained staff of attendants, and the massage, electrical-therapy, and douches carried out by a qualified staff of operators.

In every respect the hydrotherapy treatments aim at a restoration of function, and the measures employed are, for the most part, re-educative.

In connection with the Rotorua Spa is a sanatorium of seventy beds, where patients whose finances are restricted can receive treatment at an exceedingly moderate cost. The institution consists of cubicles and open wards. Thermal baths and massage-rooms in the building provide for the more helpless type of invalid.

From sixty thousand to eighty thousand baths are given annually, and an average of thirty thousand special treatments—massage, electrical therapy, &c.—is administered at the Rotorua Spa.

The usual course of treatment lasts from four to six weeks, and the high percentage of cures and improvements testifies to the value of the thermal mineral waters and the hydro-therapeutic treatments obtaining in this Dominion.

By far the great majority of the lakes of the South Island are dependent for their formation either directly or indirectly on the action of glaciers. They may be either small tarns high on the mountains or large lakes occupying considerable lengths of old stream-valleys which have been overdeepened by the excavating-power of ice during the Pleistocene glaciation, or lakes formed by the filling of hollows in the irregular heaps of debris laid down on a plain at the base of the mountains or in a wide open valley. Accumulations of debris may also assist the first two causes in the formation of lakes, and some may owe the initial formation of their basins to tectonic causes, but these have been modified profoundly by other influences.

Included in the first class are numerous sheets of water from the size of small ponds upwards, found in all parts of the mountain region, but especially in the high plateau regions of western Otago, and to a limited extent in north-west Nelson. To the second group belong the large lakes of the eastern watershed of the Alps and a small number which drain west, such as Rotoroa and Rotoiti in the Buller Basin, while to the last must be assigned the majority of the lakes of Westland; but Brunner and Kanieri should perhaps be assigned to the second class.

Seeing that glaciation was not so intense in the northern portion of the Island, it is not surprising that the lakes of that region are small and few in number. Attention has, however, been drawn to Boulder Lake, in the valley of the Aorere River, since it might be used for power purposes in connection with the great deposit of iron-ore at Parapara. It is only 151 acres in extent, but it lies at an elevation of 3,224 ft., and is conveniently placed for the establishment of an electric-power plant. Farther south, near the head of the Buller, are two larger lakes—Rotoroa and Rotoiti—occupying ice-eroded valleys dammed at their lower ends by moraine. The former has an area of eight square miles, and the latter two and three-quarter square miles; their heights above the sea being respectively 1,470 ft. and 1,997 ft., and the latter being 228 ft. deep.

In the valley of the Grey River are two lakes of considerable size—viz., Brunner and Poerua. These are shrunken and separated parts of a former extensive sheet of water which was ponded back behind a great glacier moraine. Lake Brunner is five miles long by four broad, has an area of 15.9 square miles, is 280 ft. above sea-level, and 357 ft. deep. It is surrounded on two sides by high wooded granite peaks, and on the other two by low ground. It discharges by the Arnold River to the Grey, but a very slight change of level would turn it into the Taramakau.

Lake Kanieri, which lies in the basin of the Hokitika River at the base of Mount Tuhua, is a beautiful sheet of water. It is five miles long by one and three-quarters wide, has an area of eight square miles, is 422 ft. above sea-level, and 646 ft. deep. It owes its origin partly to the hollow formed behind an immense morainic dam, and partly to the erosive action of the valley glacier. Farther south on the coastal plain of Westland are numerous small and picturesque lakes, wooded to the water's edge, lying behind heaps of glacial debris or in ice-eroded basins. The most notable of these are Ianthe and Mapourika, both of small size, the former with an area of only two square miles, at a height of 80 ft. above sea-level, and with a depth of 105 ft., and the latter remarkable for the fine panorama of mountain scenery, with Mount Cook in the background, which can be obtained from the shore of the lake. Along this strip of coast-line there are numerous lagoon-like expanses of water, cut off from the sea by areas of dune or of moraine, the chief of which is Mahinapua, which lies close to the Town of Hokitika. This is but 6 ft. above tide water, and has an area of one and a half square miles. The creek discharging from it is noted for the perfect reflections to be seen in the dark, peat-stained water.

On the eastern side of the main divide lie the great valley lakes which belong to the following river-basins: Hurunui—Lake Sumner; Rakaia—Lakes Coleridge and Heron; Waitaki—Lakes Tekapo, Pukaki, and Ohau; Clutha—Lakes Wanaka, Hawea, and Wakatipu; Waiau—Lakes Te Anau, Manapouri, and Monowai; Wairaurahiri—Lake Hauroko; Waitutu—Lake Poteriteri. These are all formed on the same plan; great glaciers have excavated the floor of a river-valley and have piled the debris across its lower portion, leaving a great hollow which was filled with water when the ice retreated. Even in those river-basins where no lakes now exist the traces of their former presence are evident; especially is this the case with the Waimakariri, Rakaia, and Rangitata Valleys. Besides these large lakes each valley has its quota of small ones, usually hidden away among the piles of moraine or ponded back behind shingle-fans. Among these small lakes should be noted the following: Tennyson, in the valley of the Clarence; Taylor, Sheppard, Katrine, and Mason, in the Hurunui; Pearson, Grassmere, and Letitia, in the valley of the Waimakariri; Evelyn, Selfe, Catherine, Ida, and Lyndon, in that of the Rakaia; Clearwater (or Tripp), Howard, and Acland, in the Ashburton; Alexandrina, in the Waitaki; Lochnagar, Hayes, and Moke, in the Clutha. In the valley of the Waiau there are numerous lakes of small size hidden away in bush-clad valleys, the chief of which is Mavora, which discharges into the main Waiau by way of its large tributary, the Mararoa. On the west coast of this region are also many insignificant lakes as far as size is concerned, such as Lake Ada, a well-known beauty-spot on the Milford Sound track, while farther north the McKerrow, a lake of larger size, discharges into Martin's Bay.

The only other lakes in this Island that are worthy of mention are Waihola, which occupies the lower portion of the Taieri Plain, and drains to the sea by a deep winding gorge cut through a ridge of rock-covered hills, the gorge being tidal for the greater part of its length; while on the coast immediately south of Banks Peninsula lie Lakes Forsyth and Ellesmere, both ponded back behind a great shingle-spit formed by the drift of material brought down the rivers and carried north under the influence of a strong shore current. Both are very shallow and liable at times to be invaded by the sea. Ellesmere is sixteen miles long by about ten broad, and Forsyth is about six miles long by one in breadth.

Among all these lakes three stand pre-eminent for their scenic interest—Wakatipu, Te Anau, and Manapouri. The first-named is walled in on both sides by steep mountains which rise at the head of the lake to over 8,000 ft. in the Humboldt Range, and to over 9,000 ft. in Mount Earnslaw. Te Anau has an uninteresting eastern shore, but its western shore is broken into three great arms, whose impressive scenery is strongly reminiscent of that of Milford Sound and George Sound; while Manapouri, with its many bush-clad islets and its indented shore-line with innumerable sheltered coves and pebbly beaches, belongs to the same type as Dusky Sound, the most beautiful of all in the fiord region.

The lakes of Canterbury lie in a treeless area and owe their scenic interest principally to the background of snowy peaks, while Wanaka and Hawea are intermediate in character between them and the more southern lakes of Otago.

These lakes are enormous reserves of energy awaiting development. Estimates of the amount available are somewhat uncertain in their upward limits, seeing that modifications of proposed schemes may increase the possible power to a marked extent. The only one, however, which has been utilized in an adequate manner up to the present is Lake Coleridge. This yields at present 16,000 horse-power (approximately), and if the scheme be developed to its full capacity the amount will probably reach 90,000. Lake Tekapo would furnish at least 400,000 horse-power; Pukaki, 70,000; Ohau, 100,000; Hawea, 90,000; Wakatipu, 100,000; Te Anau, 90,000; Manapouri, 420,000; and Hauroko, 80,000; and there are many lakes which could very easily be adapted for smaller installations. Especially is this the case in the fiord country, where the heavy and well-distributed rainfall produces an unfailing supply of water, where lakes are placed in ideal situations as reservoirs, and deep and secure harbours provide ample facilities for the transport of manufactured products. When these are properly utilized the now wild and deserted region will become the home of industry in the Dominion, and one of the main centres of manufacture in the Southern Hemisphere. One of these lakes—viz., Monowai, in Southland—is actually being utilized at the present time as a source of energy, and it is estimated to yield a minimum of 10,000 horse-power, with a maximum of 20,000.

The following is a summary of the statistics of the chief lakes of New Zealand:—

Professor James Park writes: "Though so isolated, New Zealand contains within its narrow borders representatives of most of the Palœozoic, Mesozoic, and Cainozoic formations. Moreover, its structure is that usually associated with areas of continental dimensions; and for that reason it is often spoken of as an island of the continental type. It is a miniature continent; and the occurrence in its frame work of thinogenic (shore or shallow-water) rocks, ranging from the earliest geological epochs to the present day, is undeniable evidence that it stands on a subcrustal foundation of great stability." (N.Z. Geological Survey Bulletin No. 23, p. 24, 1921.)

The oldest rocks in New Zealand appear to be those of western Otago, where over a large area is exposed a complex of gneisses and schists, intruded by granite and other igneous rocks. The gneisses in the main are altered granites and diorites, but some of the schists, at any rate, are of sedimentary origin. A pre-Cambrian age was assigned to these rocks by Professor F. W. Hutton, but Professor James Park considers them to be probably of Cambrian age, and includes them in his Dusky Sound Series, the lower part of the Manapouri System.

Perhaps next in age to the western Otago gneisses and schists are the mica, chlorite, and quartz schists of Central Otago. In the absence of fossils, however, the age of these rocks is uncertain. Professor Hutton regarded them as pre-Cambrian, Professor Park assigns a Cambrian age, whilst Dr. P. Marshall considers them to be little, if at all, older than the Triassic. Recent field-work by the Geological Survey, however, strongly suggests that an unconformity separates the Triassic rocks of the Nugget Point district from the greywackes of the Balclutha district, which overlie the Otago schists. The weight of evidence, therefore, is strongly in favour of a Palœozoic age. Some schistose rocks in north, central, and western Nelson may be as old as, or even older than, the Otago mica-schists. The gneisses and schists on the western side of the Southern Alps may for the present be classed with the Nelson schists.

The oldest known fossiliferous rocks in New Zealand are the Ordovician argillites ("slates"), greywackes, and quartzites occurring near Collingwood (Nelson), and Preservation Inlet in south-west Otago. Ultimately these rocks may be found to have a considerable development in various parts of Nelson and Westland.

Rocks containing Silurian fossils occur in the Mount Arthur, Baton River, and Reefton districts, Nelson. They are principally altered limestone, calcareous shale or argillite, sandstone, and quartzite.

Considerable areas have been assigned to the Devonian period by Mr. Alexander McKay, but owing to the non-discovery of recognizable fossils definite proof of age is wanting. For a similar reason the age of most of the rocks placed in the Carboniferous period ("Maitai Series") by McKay is uncertain. At Reefton the supposed Carboniferous rocks, which here contain many auriferous quartz-veins, are almost certainly of Ordovician age. In the typical locality near Nelson the fossils found in the Maitai rocks, according to Dr. C. T. Trechmann, indicate a Permo-Carboniferous age.

So far Permian rocks have not been satisfactorily identified in New Zealand. Park, however, considers his Aorangi Series to be of Permian age. The Maitai rocks near Nelson perhaps belong to the Permian rather than to the Permo-Carboniferous.

During some of the Palæozoic periods it is conjectured that New Zealand formed part of or was the foreland of a large land-mass that extended far to the west. This land-mass possibly persisted to late Palæozoic times, and may have been the now dismembered and all-but-lost continent known to geologists as Gondwanaland.

As yet the early and middle Mesozoic rocks of New Zealand have not been clearly separated by means of unconformities or fossil evidence into distinct formations. What may be called a Trias-Jura system is extensively developed in both the North and South Islands. The most fossiliferous localities are Hokonui Hills (Southland), near Nugget Point (Otago), Wairoa Valley, near the City of Nelson, Kawhia Harbour, and Waikato Heads, the two last-mentioned localities both on the west coast of Auckland. A broad belt of Trias-Jura rocks extends through western Canterbury and Marlborough, and is continued as a somewhat narrower belt on the north side of Cook Strait from Wellington to the Cape Runaway district. Rocks of much the same age occur in the Mokau River watershed, in the Lower Waikato Valley, in the Coromandel Peninsula, and in North Auckland.

Cretaceous rocks extend in a not-quite-continuous belt from Cape Campbell in Marlborough to the neighbourhood of Waipara in North Canterbury. At Amuri Bluff they are richly fossiliferous. To the Cretaceous belongs a somewhat extensive belt of rocks near the east coast of Wellington and southern Hawke's Bay. A continuation of this belt extends from a point north-west of Gisborne to the East Cape district. In North Auckland Cretaceous rocks cover considerable areas, which as yet have not been satisfactorily defined.

The oldest known workable coal-seams in New Zealand probably occur in Cretaceous rocks. Much controversy, however, concerning the age of our coalfields has arisen. The late Sir James Hector, and with him Mr. Alexander McKay, considered that the coal-measures belonged to a Cretaceo-Tertiary system that extended from the Upper Cretaceous to the Middle Tertiary. For many years Mr. McKay was practically the sole exponent of this theory, but since 1911 Dr. Marshall has advocated a very similar view. The truth, however, seems to be that the coal-measures concerning which there is a dispute are of two different ages. The Kaitangata, Green Island (possibly only, in part), Shag Point, Malvern Hills, and Broken River (Canterbury) coalfields are probably of Upper Cretaceous age. The other coalfields, as mentioned below, are Tertiary.

Although there is certainly a palæontological break between the Upper Cretaceous (Waipara Series) and the Early Tertiary, the existence of an unconformity, as may be inferred from the previous paragraph, is still a controversial matter. The subdivision of the Tertiary strata, which are well represented in New Zealand, is as yet more or less tentative. To the Eocene may be assigned the coal-measures of the Taratu-Milton, Grey, Buller, and Collingwood districts, and some of the coal-bearing patches of central Nelson. In various other localities possible Eocene coal-measures occur. The Wangaloa beds, near Kaitangata, contain an Early Eocene fauna, which has also been identified at Boulder Hill, North Taieri, near Dunedin, and are underlain by the Taratu-Milton coal-measures.

During the Early Eocene, as some geologists and biologists believe, New Zealand was again part of a continental area that extended far to the north, and was joined, or all but joined, to New Guinea and northern Australia. This continent may have included much of the area in the Pacific now studded with coral islands. Its former existence is inferred mainly from various features in our plant and animal life. According to Mr. T. F. Cheeseman, no fewer than 306 New Zealand plants are found also in Australia. More significant, perhaps, is the occurrence of many closely related species and genera in the two regions, for comparatively few of the 366 species are likely to have persisted since the Eocene. Many of our birds show marked affinities to Australian and Malayan species. In this connection an interesting line of support for a Tertiary extension of New Zealand to the north is afforded by the annual migrations of the New Zealand cuckoos and of the godwit.

During the Miocene period New Zealand subsided until little of the present land-surface was above water. Consequently, notwithstanding extensive denudation in later periods, Miocene strata are well represented in almost all parts of the country. They are typically developed in the Oamaru district (north-east Otago), and hence Hutton's name of "Oamaru Series" is generally applied to the Miocene strata of New Zealand. There is reason to think, however, that the lower part of the Oamaru Series is of Oligocene and even earlier age, but, until palæontological work now in progress is completed, a definite opinion cannot be expressed. Miocene rocks are well represented in north Westland, an area in which a decided unconformity separates them from the Eocene coal-measures. They form much of the surface of the North Island, where the name "papa" is commonly applied to the calcareous claystones and argillaceous sandstones which there form a great proportion of the Miocene rocks. In many places the Oamaru Series is characterized by the development of a fairly thick, soft, fossiliferous limestone about the middle horizon. This marks the time of greatest subsidence, or rather the time when the Miocene sea was deepest. Owing to their calcareous nature, the so-called Miocene rocks give rise to some of the richest agricultural districts in New Zealand. In places they contain, in their lowest horizon, seams of good brown coal. There are also brown coals of late Miocene age.

In many localities the Miocene rocks pass without visible unconformity into strata considered to be of Pliocene age. In the Hawke's Bay and Wanganui districts these are marine and highly fossiliferous. They give rise to much good agricultural and more especially pastoral land adapted to sheep-farming or dairying. In Nelson and north Westland the Pliocene strata are largely composed of river-transported material, and are known as the Moutere Gravels. These in places are poorly auriferous. In Nelson they form a poor pastoral soil, but one well adapted for apple-culture.

Towards the close of the Miocene and during the Pliocene period many parts of New Zealand, more particularly in the South Island, underwent elevation. As a result the North and South Islands (then quite different in outline from their present configuration), together with most of the outlying islands now in existence, such as the Chathams, Auckland Islands, &c., must have formed one large land-mass, which probably was united to, or almost reached, an Antarctic continent. Since many New Zealand plants^* are identical with, or closely allied to, South American forms, and there are also some striking resemblances in bird and other forms of animal life, it is thought that this Antarctic continent formed a bridge, probably at no time quite complete, between New Zealand and South America. By this route, in all likelihood, came the now extinct moas or their ancestral forms. At the time of this continental extension the Southern Alps rose far above their present heights, and were covered with one vast snowfield that fed immense glaciers spreading far and wide over the lowlands to the east and the west. According to Park, during the Pleistocene there was one great sheet of ice over the whole of the present South Island and over part of the North Island. Moreover, this ice-sheet was joined to the Antarctic ice. The extreme views of Professor Park are not shared by other New Zealand geologists, who, however, unanimously agree that a large area in the South Island was glaciated. The great ice-streams of Pleistocene times gave rise to rivers that carried enormous quantities of gravel and finer material derived from the mountains beyond the ice-front, and in great measure built up the lowlands of Canterbury and Westland. In the latter district the gravels sorted by these streams are in many places richly auriferous, but a greater and more permanent source of wealth is furnished by the fertile soil of the Canterbury Plains.

In many parts of Otago, Canterbury, Westland, and Nelson evidences of past glacial action are afforded by huge moraines, perched blocks, ice-worn surfaces (roches moutonees), rock-benches, rock-basins, and other tokens of glaciation. To ice-action, it may here be mentioned we owe some of the most magnificent features of the western Otago sounds.

At or before the end of the Pleistocene period the mountains lessened in height, through both denudation and a well-marked subsidence of the land. The climate grew milder, and the lowland ice melted away. The mighty glaciers rapidly retreated, geologically speaking, and are to-day represented only by the comparatively modest valley and mountain glaciers of north-west Otago, Canterbury, and Westland, with which may be included the small but permanent snowfield and glacier on Mount Ruapehu. While the glaciers were retreating, the rivers of Canterbury and Westland, swollen by the melting ice, were unusually active in transporting debris to the lowlands and the sea-coast. At this time, too, as well as at somewhat earlier periods, the volcanoes of the North Island furnished an abundant supply of fragmentary material, much of which was transported by the streams and used in building plains and river-flats. Many of these are fertile, but in those districts where pumice abounded a poor soil, difficult of utilization, has resulted. Thus the land gradually became much as we see it now. In recent times geological changes, such as the lowering of heights by denudation, the filling of lakes by sediment, the outward growth of coastal plains in some places, and the wearing-away of the shores in other places, have slowly proceeded, and are to-day, of course, still going on. Slow movements of the land arc probably in progress, but these have not been certainly detected. In 1855, however, as the result of a violent earthquake, the northern shore of Cook Strait, near Wellington Harbour, was raised on the average at least 5 ft., whilst the southern shore near Tory Channel and towards the mouth of the Wairau River was almost correspondingly depressed.

^*According to T. F. Cheeseman's "Manual of the New Zealand Flora" (preface, page ix), 108 New Zealand plants extend to South America.

In the preceding paragraphs little notice has been given to igneous rocks or to volcanic action. The oldest igneous rocks of New Zealand are probably represented by the gneisses of western Otago, which, as previously stated, are mainly metamorphosed granites and diorites. Plutonic rocks intrude many of the Palæozoic and Mesozoic strata, and some of the formations also show evidence of contemporaneous volcanic action. Of the more ancient plutonic rocks granite is the most prominent. It occurs in many localities in Stewart Island, western Otago, Westland, and Nelson. It has, however, not been found in situ in the North Island, though in at least six localities boulders of granite and allied rocks, probably derived in all cases from ancient conglomerates, have been discovered. Ultra-basic igneous rocks, now largely altered to serpentine, occur in north-west Otago, Westland, and Nelson.

Throughout the greater part of the Tertiary periods volcanic action in New Zealand was probably more intense than in any former age. During the Late Eocene or Early Miocene period eruptions, at first principally of andesitic rocks and later of rhyolite, began in the Coromandel Peninsula, and with little intermission continued throughout Miocene and Pliocene times. These volcanic rocks contain the gold-silver veins which have been extensively worked at Coromandel, Thames, Waitekauri, Karangahake, and Waihi.

There are many areas of Miocene volcanic rocks in North Auckland, and near the City of Auckland numerous small volcanoes were in action during the Pleistocene, or even later. Some of these—for example, Mount Rangitoto—have possibly been active within the last few thousand years. In Taranaki the beautiful cone of Mount Egmont was built up during Pliocene and Pleistocene times. It is in the central part of the North Island, however, that the most intense volcanic activity has been displayed. Volcanic rocks, more especially the pumice ejected during the Pliocene and Early Pleistocene, cover large areas. Vulcanism has not yet ceased, for minor eruptions of fragmentary material still take place from Ngauruhoe, a typical volcanic cone near Ruapehu. The most striking evidence of volcanic action, however, is afforded by the numerous steam-vents, hot springs, and geysers found in a belt extending from Ruapehu to White Island (in the Bay of Plenty), itself a volcano in the solfataric stage. It is more than a coincidence that this belt is in line with the Southern Alps. Solfataric action is generally regarded as a sign of dying vulcanism, but that the subterranean forces are still capable of mischief was shown by the eruption of Tarawera, an apparently extinct volcano, on the 10th June, 1886. On that occasion over a hundred lives were lost.

In the South Island vulcanism is apparently quite dead, for the hot springs of Hanmer Plains and the western side of the Alps are due to other causes. During the Miocene, however, volcanic outbursts took place in many localities, in some on a grand scale. Banks Peninsula is formed mainly of basaltic and andesitic rocks Lyttelton and Akaroa Harbours are believed to represent ancient craters or centres of eruption. In the neighbourhood of Dunedin occurs a very interesting series of alkaline volcanic rocks. These were first described by the late Professor G. H. F. Ulrich, and in later years Dr. Marshall has given them much study. Recently alkaline volcanic rocks have been discovered in the outlying Chatham Islands.

In the course of a short article it is impossible to give any adequate idea of what has been accomplished by geological workers in New Zealand, or what remains yet to be done before even the foundation for future work shall be securely laid. The important applications of geology to agriculture and mining have hardly been mentioned, but elsewhere in this volume will be found descriptions of the agricultural and mineral resources of the Dominion. For detailed information the reader is referred to the bulletins of the New Zealand Geological Survey; to Professor Park's "Geology of New Zealand," which contains an excellent bibliography; and to the treatises on "Geology of New Zealand," by Dr. Marshall, as well as to many other publications too numerous to be here named. Finally it may be mentioned that in each of the University Colleges at Auckland, Wellington, Christchurch, and Dunedin excellent instruction in geology is being given by capable and enthusiastic teachers, so that in the near future we may expect increased progress in solving the many knotty problems of New Zealand geology.

Since 1888 there has been established in New Zealand a system of observing local earthquakes at selected telegraph-stations—about eighty in number—distributed throughout the extent of the Dominion.

Whenever a shock occurs and is felt by an officer in charge of one of these stations he fills up a form giving the New Zealand mean time of the beginning of the shock, its apparent duration and direction, and the principal effects observed by him. Some of the officers exhibit considerable care and skill in making up these returns, and the data have been used to determine principal origins of earthquakes within the New Zealand region.

All observers of earthquakes are cordially invited to forward their reports to the Government Seismologist, Hector Observatory, Wellington, giving all or any of the following particulars:—

The Rossi-Forel scale of earthquake intensities is as follows:—

^*A convenient means of verifying the time is provided by the wireless time-signals sent out every day, except Sundays and Government holidays, at 10.30 a.m. N.Z. time, by the Hector Observatory on a wave-length of 600 metres.

The New Zealand returns are valuable not only in themselves, but as part of a world system of seismological observations; and the attention of observers is called to the fact that the reliable character of the record depends upon the individual accuracy of each observer. No shock, however slight, should be omitted. It is especially important that the first two questions should be answered accurately

Three seismographs, all with photographic registration, are installed in New Zealand: two are Milne horizontal pendulums, and one is the new Milne-Shaw horizontal pendulum. One Milne and the new Milne-Shaw seismographs are installed at the Hector Observatory, Wellington, with their booms placed at right angles; and the other Milne seismograph is installed at the Magnetic Observatory, Christchurch.

The records of the New Zealand stations are sent to the General Secretary of the Seismological Committee of the British Association, to the Station Centrale Sismologique, Strasbourg, France, and to the principal observatories of the world, and thus form part of the general system of earthquake-observation being conducted throughout the world since 1890.

The accompanying diagram illustrates graphically the number and intensities of the earthquakes reported to the Seismologist in the years 1921, 1922, and 1923. These reports were supplied by officers of the Post and Telegraph Department, by private observers, and by the newspapers. Each vertical line represents the maximum effect of an earthquake, with the intensities according to the Rossi-Forel scale shown at the sides of the figure. It will be seen that two earthquakes in 1921, and four in 1922, reached intensity VIII on this scale. The figure also shows the distribution in time of the earthquakes.

Deaths due to earthquakes in New Zealand are fortunately very few. In the last seventy-five years seven have been recorded.

The shock of October, 1848, threw down a wall in Wellington, and three people were killed.

On the 24th January, 1855, a death occurred at Wellington recorded as "accidental death from the falling of a chimney." The large earthquake took place during the night of the 23rd January, 1855.

On the 16th November, 1901, a child was killed by the Cheviot earthquake.

On the 12th April, 1913, a Maori was killed at Masterton by material falling from the post-office, due to an earthquake.

On the 7th October, 1914, a shepherd was killed by the Gisborne earthquake.

The climate of the Auckland Province, speaking generally, combines degrees of warmth and humidity agreeable by day and comfortable by night. North of Auckland City conditions are almost subtropical, and in summer balmy easterly breezes prevail, and are responsible for delightful conditions. In winter the winds are more north and west, while changes to the south-west or south-east mostly account for the rainfall. Cumulus clouds are frequently formed in the afternoons, and, while tempering the heat of the day, also cut down sunshine records somewhat, but add considerably to the beauty of the land- and sea-scape. Southward of Auckland the climate is more varied, the west coast experiencing more rain, while the central parts are warmer in the day and considerably colder at night. In the winter months frosts, which are unknown farther north, now and then occur in the hours of darkness. Eastward from Rotorua (the groat health resort and centre of the thermal region) is to be found one of the most genial climates in the world, and Tauranga and Opotiki have charms all their own, especially for their weather and the fruits which ripen to perfection in these regions.

The monthly and annual means of the temperature, rainfall, and sunshine of Auckland and Rotorua are shown in the following tables:—

The Hawke's Bay Province is one of the richest in New Zealand, and is favoured with a pleasant climate, being sheltered from westerly winds, though occasionally they are of the warm and dry (Foehn) type. It is rather dry, but ex-tropical disturbances are occasionally responsible for heavy downpours. Though the number of days with rain is less than, and sunshine above, that of other parts, the rainfall is still a good one, and fairly regular throughout the year, though some seasons have been notably dry. The meteorological records of Napier show reliable normals for the coastal districts. Inland the country is rather mountainous and less mild

Wellington, the capital city, as disclosed by its meteorological records, has a mean climate for the whole Dominion. Wellington occupies a central position, and is situated near Cook Strait, which divides the two main Islands. It has a somewhat changeable but temperate climate, and, though occasionally subject to disturbances from warmer regions, is usually controlled by the terrestrial wind-currents which have a westerly direction round the world in the latitude of the "forties." It is popularly regarded as a rather windy spot, for high winds are frequently experienced, although they hardly ever reach hurricane force. Its windiness is largely owing to local configuration, for places quite near Wellington experience very little wind; and to compensate for this rather disagreeable element is a bountiful sunshine, averaging 2,022 hours per annum. There is a plentiful rainfall, amounting to nearly 50 in.

The region between Wellington and Taranaki, following the Taranaki Bight, is probably as fertile and agreeable as any in Australia or New Zealand; but inland, though very productive, conditions are not so favourable.

Taranaki has a rather heavy rainfall, and in most parts of this region the grass is always green. Its climate is mild, and cattle winter in the open. Wanganui and Manawatu districts (which lie between Wellington and Taranaki) have less rainfall than either Wellington or Taranaki.

It may be useful to make a comparison between the records of Wellington and those of Camden Square, London.

Nelson and Marlborough are highly favoured regions with regard to sunshine and shelter from marine winds. Long ago Bishop Selwyn said, "No one knows, what the climate is till he has basked in the almost perpetual sunshine of Tasman's Gulf, with a frame braced and invigorated to the full enjoyment of heat by the wholesome frost or cool snowy breeze of the night before."

Pastoral and agricultural industries are thriving, and the Province of Nelson is also famous for its fruit cultures—apples especially being celebrated for their variety, colour, and flavour. The rainfall about Nelson is very reliable, and averages from 35 in. to 45 in. per annum. Marlborough is also a sunny province, and its rainfall averages from 25 in. to 30 in.

Following are the rainfall and sunshine records for Blenheim:—

The climate of Westland is influenced by its position with regard to the prevailing westerly winds, its proximity to the sea from which these winds blow, and the mountainous character of its eastern half. The rainfall, as might be expected, is heavy, and ranges from about 70 in. per annum in the north on the coast to as much as 200 in. in the mountainous country. The weather-changes are chiefly due to atmospheric depressions, with lowest pressures passing south of the Dominion. Cyclones centred in the north, while bringing heavy rains to the North Island and the east-coast portions of the South, do not, as a rule, affect Westland, as easterly winds, which then prevail, are not conducive to cloud-formation in this province. Sunshine at Hokitika averages 1,897 hours a year, and, though not so abundant as in east-coast districts, th is a good average amount considering the rainfall. Westland is noted for a clear, beautiful atmosphere during fair-weather periods.

The chief health resort of the South Island, Hanmer Spa, is situated on a small plateau in the northern portion of the Canterbury Land District. On account of its altitude, 1,120 ft., it enjoys an invigorating climate, with a mean annual temperature of only about one degree below that of Christchurch. Owing to its elevated position and nearness to the mountains Hanmer is in some winter seasons subject to rather severe snowstorms, such as are never experienced on the Canterbury Plains. The mean annual rainfall is 38.15 in., and the mean total sunshine 1,992 hours.

The district of Canterbury comprises a variety of topographical features. A plain stretches over a hundred miles from north-east to south-west, with a maximum width of about forty miles from the east coast to the foothills to the westward. The latter merge into the mountainous country culminating in the main range of the Southern Alps, which divides the provinces of Canterbury and - Westland, and affords a protection from the heavily moisture-laden north-westerly winds. The rainfall of the Canterbury Plains is in consequence much restricted, the average being about 26 in. There is, however, a remarkable progressive increase from east to west, as is shown by the records. At Christchurch the mean is 25.13 in.; at Mount Torlesse Station (near Springfield), 39.86 in. The climate of Canterbury might almost be described as Continental in type, with large extremes of temperature between summer and winter and between day and night. Except in the three summer months frosts are numerous, and even in the early spring and late autumn they are at times severe enough to damage vegetation of a tender nature. In summer, day temperatures of over 90° in the shade are sometimes experienced. With regard to both climate and soil, the Plains have proved most suitable for agricultural farming, and much of the district is capable of growing splendid cereal and root crops. The prevailing winds in Canterbury are north-east and south-west, while north-westerlies are not, as often supposed, of frequent occurrence. They are most common in the springtime, and, being dry and warm, they have a somewhat enervating effect, though in winter-time they come as a welcome change from the keen temperatures then generally ruling. The bright sunshine, as recorded at Lincoln, shows a daily average for the year of 5.8 hours.

Otago, the southernmost part of New Zealand, is very diversified as regards both its physical features and its climate. Inland, in Central and North Otago, the climate is dry and clear—hot in summer and cold in winter. The rainfall for this district averages from 13 in. to 20 in. Near the coast, in the Dunedin district, the rainfall is more plentiful, averaging from 30 in. to 40 in. per annum, a good deal of which falls in light drizzling rains.

There are continuous rainfall records from various parts of Dunedin for seventy years, of which the median rainfall is 33.5 in., and the mean in the table following may be regarded as too high.

The total year's rainfall was above the average over the North Island, except at a few places in the central region and along the west coast southward of Kawhia. In the South Island the west-coast districts and South Canterbury recorded a deficiency, while the north-east districts and Otago had an excess.

Following is a short summary for each month of the weather and the chief atmospheric systems which were in evidence:—

January.—Throughout the greater part of the Dominion January was abnormally wet, and rainfall totals in most cases were considerably in excess of the average. Westland and Southland in the South Island were the only districts where below-normal amounts were recorded.

Some very heavy downpours accompanied the frequent electric disturbances which were experienced during the month, especially over the North Island.

Owing to the passage of ex-tropical disturbances both over and northwards of the Dominion, easterly winds predominated, with much dull and misty weather, though warm temperatures were generally experienced.

February.—With the exception of a fair-weather period between the 8th and 13th, February proved very unsettled and unseasonable on account of depressions of both tropical and antarctic origin.

Cyclonic storms passed northward of the Dominion on the 1st and 28th, and a cyclone acted in conjunction with a westerly "low" between the 14th and 16th. An intense westerly low-pressure area ruled between the 5th and 9th, and depressions of the latter type were also frequent, though generally of only moderate intensity, between the 18th and 27th.

The effect of these various disturbances is shown in a rainfall above the average over most of New Zealand. Deficiencies, however, occurred on the east coast, in the extreme north and south, and about New Plymouth in the North Island, and in the northernmost districts and in parts of Central Otago in the South Island. Wind force was higher and temperatures were lower than the normal.

March.—The early part of March was anticyclonic in character, fair weather prevailing generally until the 13th. The remainder of the month, except for short fair-weather intervals, was unsettled under the influence of various depressions passing in the South. Of the latter the most notable, an intense and extensive one ruling between the 14th and 19th, was responsible for strong west to south-west winds and rain in many parts. On the 16th the barometer fell as low as 28.95 in. at the Bluff.

The total rainfall was above the average in the northern and southern portions of the South Island and also at scattered stations on the west coast; elsewhere it was mostly below, the largest deficiencies occurring in the east-coast districts.

April.—During April there were two periods of unsettled weather—viz., between the 7th and 10th and from the 18th to the 28th. In the former period a disturbance which passed in the south on the night of the 7th developed considerable intensity to the eastward on the following day, and accounted for a heavy south-west gale. Cold and stormy conditions prevailed, especially along the east coast on the 8th and 9th, and electrical disturbances and heavy hail showers were experienced, with snow on the higher levels.

The heaviest rains, however, fell in the period 18th to 28th, when an ex-tropical disturbance dominated. Very heavy rain and floods with easterly gales occurred between the 19th and 21st in the northern half of the North Island. The centre of the storm passed in the north on the 22nd. It was followed by a "secondary," which apparently developed in the south, and caused one of the most serious floods experienced in Dunedin. In that city the total rainfall for the three days (20th, 21st, and 22nd) was 8.45 in., of which 6.81 in. fell on the 21st.

A remarkable feature about both these disturbances was that the heavy downpours were confined to comparatively small areas. This is shown in the totals for the month, which were much above the average northward of Kawhia and Gisborne in the North Island, and on the east coast between Kaikoura and Nugget Point in the South Island. All other parts of the Dominion show an aggregate rainfall considerably below the mean.

Anticyclonic conditions and fair weather were general between the 10th and 17th and on the last two days of the month.

May.—The month opened with anticyclonic conditions and fair weather, but on the 3rd there was evidence of the development of a cyclone to the westward. On the 5th the centre of the latter was located in the north, while pressure increasing in the south at the same time caused a very steep baric gradient, especially along the eastern coast. This resulted in a south-east storm, and the north-east districts of the South Island registered what, so far, constitutes a record rainfall for these parts. The heaviest rains, which occurred on the 6th and 7th, accounted for serious floods and damage. On the 6th, at Stag and Spey, Kaikoura, 16.69 in. were recorded, and at Keinton Combe, in the Waiau district, 14.40 in., of which amount 13 in. fell in twelve hours. To give some idea of the intensity of these downpours it may be mentioned that the average month's rainfall for stations in these districts is between 3 in. and 4 in.

Another, though smaller, disturbance passed in the north between the 18th and 21st, and this was followed by an extensive westerly low - pressure area. This depression brought very unsettled conditions, especially in and southward of Cook Strait, and some very heavy rains to the west-coast districts of the South Island between the 22nd and 27th. Otira recorded a total of 40.33 in. for the month, which mostly fell in the latter period.

The aggregate rainfall was above the average in all parts of the Dominion, except in Southland district and in the vicinity of the towns of Auckland and New Plymouth.

The monthly temperatures recorded were above the average, and the general character of the weather may therefore be described as mild, dull, and moist.

June.—Except for one short period, between the 5th and 8th, anticyclonic pressure was almost entirely absent over the Dominion during the month of June, and the barometer was continuously below normal owing to numerous disturbances of both tropical and antarctic origin.

The effects of these disturbances were most markedly shown in the northern and west-coast portions of the North Island, and in Otago and, to a less extent, Westland in the South Island. All these districts recorded a total rainfall above the average, while the east-coast districts, particularly of the South Island, experienced a deficiency, with fair weather and an absence of high winds.

Snow fell on several days in the high country, and the southern hills were covered to a greater extent than is usual under normal winter conditions.

July.—July was characterized by cold, dull, and damp weather, although the total rainfall was below the average over the greater part of the Dominion. An excess was experienced only at a few places in the northern and east-coast districts of the North Island, and in North Canterbury in the South.

A westerly depression between the 1st and 6th accounted for heavy and widespread falls of snow in the highlands of the South Island.

From the 7th to the 9th anticyclonic conditions and fair weather prevailed, and this was the only period during which such conditions were general. The remainder of the month was very dull, misty, and showery, but heavy rain fell on the 14th and 15th in the northern and east-coast districts of the North Island, owing to the passage of a cyclone centred northward of New Zealand.

The barometer rose very high towards the close of the month, but the weather, though fine over most of the country, continued cold and showery with strong south-easterly winds in the east-coast districts. This was accounted for by a disturbance which persisted in the neighbourhood of the Chatham Islands on the edge of the anticyclone.

August.—In nearly all parts of the Dominion the total month's rainfall was considerably below the average, the only portions having an excess being along the east coast between East Cape and Cape Palliser and the south-west corner of Otago.

Southerly winds predominated, but they usually accounted for only light rainfall in spite of the number of atmospheric depressions which passed over or within effective range of the country.

The weather during the month was changeable, and cold frosty nights were frequently experienced. Sunshine, however, was more prevalent than during the two preceding winter months, owing to several anticyclones which ruled.

Three westerly disturbances occurred during the month, the longest influencing weather conditions for about ten days from the 13th. A southerly gale on the 21st and 22nd was particularly severe along the east coast of the South Island and about Cook Strait.

Ex-tropical disturbances passed in the north on the 10th and 24th, and the former accounted for heavy rain on the east coast of the North Island between the 10th and 12th.

Some further snowfalls occurred on the high country of the South Island, but warm winds and rain during the last few days were responsible for considerable thawing and a consequent rising in many of the rivers and creeks in the south.

September.—During September there were two periods—viz., between the 2nd and 8th and between the 24th and 30th—when anticyclonic pressure ruled and fair weather was experienced generally. Though conditions were somewhat unsettled between these two periods, general heavy rains occurred only from the 9th to the 12th, when a widespread cyclone held sway.

Two distinct westerly disturbances passed in the south on the 17th and 23rd respectively, and a cyclone passed off East Cape about the 19th.

Rainfall was in excess of the normal northward of East Cape and Kawhia in the North Island, and in the Nelson and Blenheim districts and about Greymouth, Hokitika, and Arthur's Pass in the South Island. In all other parts of the Dominion there was a deficiency.

The general character of the weather may be described as dry, warm, and fair, which, with the occasional spring showers, was favourable to abundant vegetable growth.

October.—With the exception of three short periods—viz., between the 1st and 3rd, 18th and 21st, and 25th and 30th, when anticyclonic conditions ruled—the weather of October was dominated by frequent westerly depressions and at least three ex-tropical cyclones. As a result the month was very changeable. The westerly depressions were mostly of only slight intensity, but one which culminated on the 24th was very severe. A cyclone persisting about East Cape for several days about the middle of the month caused southerly gales and stormy conditions between the 15th and 17th, particularly along the east coast.

Wide differences in rainfall occurred over the Dominion, and, though mostly above the average in the northern and east-coast districts of the North Island and in North Canterbury in the South, most other parts recorded a deficiency, many places in Nelson and Westland having less than half the usual amount.

Temperatures were generally above the average, but the cold southerly in the middle of the month was responsible for considerable damage.

November.—The few disturbances that were in evidence during November were all of slight intensity, and mainly small westerly "lows" passing in the south on the southern edge of anticyclones centred northward of New Zealand.

As a result winds were chiefly from some westerly quarter, bringing a rainfall above the average to a few places on the west coast of the South Island and in the extreme north of the North Island. A good fall of rain about the 16th in the Nelson and Blenheim districts also accounted for some places having a slight excess. All other parts of the Dominion recorded considerably less than the usual amount, and many districts experienced the driest November ever recorded.

The weather generally was warm and dry, and more like that of a summer month. The last few days were particularly warm, and on the east coast absolute maximum temperatures of 90 degrees and over were recorded at this time.

There was usually abundant growth in vegetation, and for the sheep and dairy farmer the month proved entirely satisfactory.

December.—Anticyclonic conditions were continuously in evidence in the north during the first half of December, and, although three small westerly depressions passed in the south, only scattered rainfall was recorded. The latter half of the month was dominated by four intense westerly "lows," and these accounted for heavy rain in the west-coast districts and high westerly winds and boisterous conditions in and southward of Coo Strait. A strong north-west gale on the 28th caused extensive damage in Canterbury.

The best and most general rainfall occurred about the 19th and 20th, but the east coast of the North Island did not benefit.

As a result of a predominance of westerly winds, only the western districts of the South Island and a few places on the west coast of the North Island recorded a total rainfall above the average. All other parts of the Dominion experienced a deficiency, which was most marked in Hawke's Bay, some stations in the latter district having no rain during the month.

The following tables show the difference, above or below the mean, for each month in the year:—

Dotted line showing the total monthly rainfall from January, 1923, to January, 1924 (inclusive).

Dotted line showing the mean monthly temperature from January, 1923, to January, 1924 (inclusive).