THE NEW ZEALAND OFFICIAL YEAR-BOOK, 1937

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 Now 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 principal treatment establishments are the Main Bathhouse and the Ward Baths.

In the Main Bathhouse are a series of private bathrooms, slipper and step down, each with its dressing-room attached, and a couch for packing purposes. The baths are arranged for either “Priest” or “Rachel” waters, with under current douches and showers. There are, also, deep “Priest” pools at suitable temperatures for the treatment of chronic cases.

Off the main hall are treatment-rooms where massage and every variety of physiotherapeutic treatment can be given, and, in either wing of the building, a complete establishment for Aix-Vichy douche massage.

The Ward Bathhouse is a handsome new block of buildings which has replaced the old Pavilion Bathhouse. This building, divided into convenient sections for service and control, consists of a large main hall, swimming-pools, hot “Rachel” “pools”, “Old Priest” and “Radium” Dr. A. S. Herbert, O.B.E., M.D., gives the following grouping of the better-known waters corresponding roughly to their mineral-water classification:—

Sulphur waters: Rotorua, Hanmer, Taupo, Wairakei, Waiotapu.

Alkaline waters: Te Aroha.

Saline waters: Helensville, Waiwera, Tarawera.

Iodine waters: Morere, Te Puia.

Calcium carbonated waters: Kamo.

Simple thermal waters: Okoroire and the Waikato springs.

The following article is by the Government Balneologist, Dr. J. D. C. Duncan, M.B., Ch.B. (Edin.), Member of the International Society of Medical Hydrology, Fellow of the Royal Society of Medicine, and Fellow of the Royal Geographical Society:—

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 Now 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 principal treatment establishments are the Main Bathhouse and the Ward Baths.

In the Main Bathhouse are a series of private bathrooms, slipper and step down, each with its dressing-room attached, and a couch for packing purposes. The baths are arranged for either “Priest” or “Rachel” waters, with under current douches and showers. There are, also, deep “Priest” pools at suitable temperatures for the treatment of chronic cases.

Off the main hall are treatment-rooms where massage and every variety of physiotherapeutic treatment can be given, and, in either wing of the building, a complete establishment for Aix-Vichy douche massage.

The Ward Bathhouse is a handsome new block of buildings which has replaced the old Pavilion Bathhouse. This building, divided into convenient sections for service and control, consists of a large main hall, swimming-pools, hot “Rachel” “pools”, “Old Priest” and “Radium” baths, and a block of private “Rachel” baths.

At the back of these buildings is an attractive sunken courtyard, with fountain and formal garden, surrounded on three sides by verandas, and on the fourth by an open pergola facing the lake. In this courtyard garden patients and visitors can bask in the sunshine, protected from prevailing winds.

The swimming-pools, open to the air, are spacious baths lined with white tiles and having douches, showers, and convenient dressing-cubicles. These provide recreational facilities for patients and visitors.

The “Radium” and “Priest” baths, built on the pumice bed of the soil, contain some of the most important therapeutic waters in existence, and are invaluable in the treatment of heart conditions and cases of nervous debility. In connection with these baths are comfortable rest-rooms and convenient massage establishments.

The private baths are of the porcelain, slipper variety, and step-down tiled baths—the latter designed for helpless or crippled patients.

The swimming-pools of the new Blue Bath afford one of the most attractive playgrounds for visitors to Rotorua. There are two pools, set in T form with a colonnade between. The larger pool, 100 ft. by 40 ft., with a depth of 4 ft 6 in. to 9 ft., has unique diving-platforms. This pool is lighted under the water by twenty are lamps, which give a beautiful luminous effect to the water. The smaller pool, 70 ft. by 36 ft., is a safe and enjoyable playground for children of any age. Both pools are lined with white tiles. Convenient dressing and shower rooms surround the pools. At the entrance a luxurious lounge provides a resting-place for bathers, and above this an attractive tea-room serves refreshments to its patrons.

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 Czechoslavakia, 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 hyperemia 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 confined within pools on the natural pumice-bed, and, by a primitive arrangement of wooden sluice-valves, are 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 deal only 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. to the square inch, 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 (Germany). 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 hyperæmic 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 mud baths being highly impregnated with silica, which has a bland, sedative effect on the tissues, are particularly indicated in cases of acute or subacute neuritis, gout, and certain skin conditions. The action of these baths is to induce an active hyperæmia in the patient with an actual absorption of free sulphur, which is present in considerable quantity. Also the radio-activity of this medium (0·185 per c.c.) is possibly an active factor in the therapeutic action of these baths. In some of the cases undergoing mud-bath treatment the effect has been almost miraculous—instant relief from pain; reduction of swelling caused by inflammatory exudates—and such patients have been able to discard crutches or other adventitious aids and to walk with more or less normal comfort.

Perhaps, of more recent date, the most efficacious effects of mud treatments have been manifested in cases of skin conditions—notably psoriasis: cases which have resisted all forms of drug treatment have cleared up in an almost magical manner; and so frequently have such cures been effected that one believes that the silicious mud of Rotorua has some markedly specific action as a therapeutic agent.

The treatment of gout depends entirety 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 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 about thirty thousand special treatments—massage, electrical therapy, &c.—are administered each year 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.

New Zealand is a small country, but its geological history is as complex and as ancient as that of a continent. Land, though from age to age it varied greatly in area, outline, and elevation, must have persisted in the New Zealand area from the oldest Palæzoic or earlier. Long periods during which gentle regional oscillations and warpings, aided by the slow-acting forces of denudation, brought about gradual changes were interrupted by great revolutions, when earth-stresses ridged the crust into mountains and quickly altered the whole configuration of the land and sea-floor. For New Zealand the important geological periods are those that followed the two latest mountain-building movements—the Kaikoura deformation of late Tertiary time, and the Hokonui deformation of the early Cretaceous. The deposits laid down in the intervening period of relative crustal stability cover a large proportion of the land, and contain all the coal and most of the limestone of the Dominion. The soils on which grow the forests, pastures, and crops are of post-Tertiary age, and the great bulk of the gold has been won from deposits formed during the same period.

The oldest known fossiliferous rocks in New Zealand are the Ordovician slates and greywackes of west Nelson and south-west Otago. Lower unfossiliferous beds of the same great system extend southward from the northern area and outcrop in the Westport, Reefton, Greymouth, Ross, and Okarito districts. Above the fossil-bearing beds, but probably also of Ordovician age, are the black phyllites, quartzites, and marbles which outcrop continuously from Takaka to Mount Owen, and are again exposed in the upper basins of the Matakitaki, Maruia, and Grey Rivers. The similar rocks of western Otago probably also belong to this group. The complex of gneisses and schists of the same region, intruded by acid and basic plutonics, and usually considered of Archaean age, resembles the part of the Ordovician strata of western Nelson that has been similarly invaded and metamorphosed and may well be of early Palaeozoic age. Different authorities assign the mica, chlorite, and quartz schists of Central Otago to ages that range from the Archaean to the Triassic. They are certainly Palaeozoic or older, since they grade upward into greywackes that, at Clinton, contain Permian fossils.

Devonian rocks are certainly known only in the Baton, Wangapeka, and Reefton districts. These beds, fossils from which have lately been examined in England, cover only small areas. Rut the old Geological Survey mapped wide tracts of country in Nelson and Otago, covered with beds of the Te Anau Series, as Devonian, and the correlation may well be correct, though the rocks are entirely unfossiliferous.

The Maitai Series, which forms the ranges on the south-east side of the Nelson lowlands, are probably of Carboniferous or Permo-Carboniferous age. Their position in the time scale and their correlation with rocks in other parts of New Zealand have provoked much discussion. Permian strata, as already stated, occur in Otago, where the area they cover may be considerable.

Richly fossiliferous late Triassic rocks are known in the Kawhia-Mokau district, near the City of Nelson, and at several localities in Canterbury and Otago. Except in Nelson and Canterbury, strata that contain fossils referable to several stages of the Jurassic succeed without observed unconformity. The broad belt of greywacke and argillite that forms the mountains of Canterbury and Marlborough, and continues as a narrower belt through Wellington to northern Hawke's Ray, is usually referred to the Trias-Jura. Similar rocks outcrop in the centre of the North Island and at many points in North Auckland. There are Upper Triassic molluscs in these beds at several localities, and the vertebra of a saurian with Triassic rather than Permian affinities was found near Wellington. Lithologically the greywackes and argillites of this vast series differ somewhat from the rocks of similar type belonging to the Jurassic and Maitai series; they are therefore thought to be of older Triassic age, but may well range into the Permian. The schists occurring with them in the Kaimanawa, Kaikoura, Moorhouse, and Kirkliston Ranges are probably older.

The thick conglomerates conformably overlying the younger Jurassic shales of the Port Waikato, Kawhia, and Coromandel regions belong to either the youngest Jurassic or the oldest Cretaceous. Strata of early and middle Cretaceous age occur east of the main axis of New Zealand at several points from Marlborough to East Cape. Late Cretaceous beds are much more widely distributed, being known in North Auckland and in many localities along the eastern side of both Islands. They contain thick layers of black shale that give many indications of oil, which, however, has not yet been found in commercial amount. The oldest known workable coal-seams in New Zealand, those at Broken River, Malvern Hills, Shag Point, and Kaitangata, and perhaps some near Greymouth, are in young Cretaceous beds.

Tertiary rocks form the greater part of the North Island and are widely distributed in the South. As a whole they are weaker and more readily weathered than the older strata, and hence have given rise to less rugged country, now mostly cleared and grassed and forming productive pastoral land.

Eocene rocks are present in North Auckland, and probably also in the Gisborne, Hawke's Ray, and east Wellington districts. In the South Island they occur on the West Coast and in Canterbury and Otago, in which regions they contain valuable coal-seams worked at Westport, Reefton, Greymouth, Mount Somers, and Milton. Of the same age are the auriferous “cements” of the Tuapeka district that greatly enriched the gravels of the neighbouring streams and are themselves worked for gold.

In Oligocene time the maximum subsidence during the Tertiary occurred, and but little of the New Zealand area remained above sea-level at its close. The thick limestones of the Oamaru district and the contemporaneous limestone prominent in many parts of New Zealand are the younger deposits of this age. The older beds contain the extensive coal-measures of the North Auckland, Waikato, Charleston, and other coalfields.

Miocene strata cover large areas in both islands, and also outcrop in the Wanganui, Gisborne and Hawke's Bay regions. In north Taranaki, the Murchison basin, and parts of the West Coast thick coal-measures of this age contain workable scams of brown coal.

During the Pliocene the New Zealand area, which had been intermittently rising since the close of the Oligocene, was greatly elevated and deformed. The earth blocks from which the present mountains have been carved were uplifted from, or from near, sea-level, and New Zealand as it now is was roughly shaped out. In the South Island the deposits of this period are chiefly gravels deposited in structural depressions; but in the North, and especially in its southern half, there are thick and extensive shoal-water marine sediments. These, and the underlying Miocene strata, are the source of the petroleum found at New Plymouth.

The Pleistocene was a period of regional oscillation. While the land was high the mountains of the South Island were intensely glaciated, and great ice-streams, carrying vast bodies of debris, descended into the low country; after the highlands had been reduced in height through both denudation and decided subsidence the glaciers rapidly retreated, and are today represented by comparatively small remnants far in the mountains. While the ice was melting, the rivers of the South Island were unusually active in transporting waste to the lowlands and the sea. At this time, too, as well as somewhat earlier, the volcanoes of the North Island ejected an abundant supply of fragmentary material, much of which was borne away by the streams and used in building plains.

The deposits of Pleistocene and Recent age are in New Zealand of greater economic importance than those of all other ages. The plains, river-flats, and low lands generally were formed or profoundly modified during this period, and the soils that cover them produced. During the same time practically all the gold won from the gravels of the South Island was liberated from a hard matrix and concentrated into workable deposits, and the rich bonanzas of the lodes of Hauraki were formed by secondary enrichment. The land-oscillations of the period are also of economic importance, for New Zealand's abundant water-power is derived from streams that have not yet, owing to the recency of land-uplift, cut their valleys to grade. On the other hand, land-depression has provided harbours and valuable artesian basins in many parts of the Dominion.

Plutonic rocks intrude many of the Palaeozoic and Mesozoic strata, and some of the formations show evidence of contemporaneous volcanic action. Of the plutonic rocks granite is much the most prominent, and it outcrops at many points in west Nelson, Westland, Otago, and Stewart Island. In Nelson there were at least two periods of intrusion, probably corresponding with the great mountain-folding movements of the late Palaeozoic and early Cretaceous times. The auriferous lodes of Reefton and other localities on the West Coast probably originated from the cooling magmas that formed the younger granites. Basic and ultra-basic rocks, the latter now largely altered to serpentine, occur in Nelson, Westland, Otago, and, to a less extent, in North Auckland.

Though volcanoes are known to have existed in Mesozoic and Palaeozoic times, they seem to have been more active during the Tertiary than in any earlier age. The vast pile of flow and fragmental rocks that form the Hauraki Peninsula and the range that continues it southward to Tauranga belong to this period. The gold-silver veins extensively worked at Coromandol, Thames, and Waihi are in these rocks, which southward are smothered by the rhyolitic pumice that vents in the Taupo-Rotorua zone ejected during the late Pliocene and Pleistocene. Thick showers of pumice from this region cover a large part of the centre of the North Island and streams have carried the finer material to practically all the low-lying parts of the island. The volcanoes are still alive, as is evidenced by the steam-vents, hot springs, and geysers found in the depressed zone extending from Ruapehu to White Island. The volcanic rocks of Taranaki probably range from the Miocene to the Pleistocene in age. The basalts and scoria cones that occur so abundantly between Kawhia and the Bay of Islands belong for the most part to the late Pliocene and Pleistocene, though cones at Auckland City are probably Recent.

In the South Island the volcanoes appear to be quite dead, for the hot springs at Hanmer and near the alpine chain are due to other causes. In the middle Tertiary, however, there were outbursts at many points, the chief eruptions being at Banks Peninsula and about Dunedin.

In a short article it is impossible to give an adequate idea of what geological workers have accomplished in New Zealand, or of what they have yet to do in order that the wisest use may be made of the country's mineral and agricultural resources. For good general accounts the treatises of Professors Park and Marshall should be consulted, and for more detailed information the bulletins of the Geological Survey and the many papers that have appeared in the “Transactions” of the New Zealand Institute (now the Royal Society of New Zealand).

Earthquake and volcanic activity are manifestations of the adjustments constantly occurring in the earth's crust. In the not far distant past, geologically speaking, a more or less continuous belt of mountains was raised up round the border of the great sunken area of the Pacific, and this belt as a whole is characterized by “chronic and acute seismicity.” At times the earthquakes occur within the belt itself, though a large proportion have their epicentres on its submerged frontal slope.

The South Island of New Zealand and the eastern part of the North Island are on the crest of the great mountain ridge or crustal fold which forms a portion of the real border of the Pacific. This ridge maintains a relatively straight course-north-north-west for 1,600 miles across the floor of the Pacific, nearly to Samoa. The Auckland Peninsula, part of a decidedly weaker fold, meets the main fold nearly at right angles in the Rotorua-Taupo volcanic region. The earthquakes of this seismically sensitive district, though they may be locally severe, are not usually felt far from their points of origin. On the other hand, the tectonic earthquakes that occur along the main earth-fold shake large areas, some of them being recorded on instruments throughout the world. These are caused by the slipping of earth-blocks against their neighbours along fractures.

Many great fault-zones have been traced for long distances, but a few only have been active since European occupation. The Hawke's Bay earthquake of 1931 raised an area sixty miles long in a north-east direction and in parts ten miles-wide. The uplift was greatest along the south-east edge of the area—for miles amounting to 6 ft. or more. Numerous levels on the Heretaunga Plain and along the railway north of Napier show that the uplift decreased north-westward, so that the area was slightly tilted in that direction. The ground east of the uplifted area sank, and parts of the Napier and Wairoa flats are over a foot lower than before the earthquake.

In 1929 movement along a north-trending fault seven miles west of Murchison raised the ground east of the fault by about 15 ft., and caused it to shift north-west by about 9 ft. The uplift gradually decreases eastward and dies out sixteen miles from the fault, facts indicating a slight tilt of the earth-block toward the east. Recent levellings show that the block is sinking somewhat irregularly, a movement, no doubt, causing some of the innumerable local after-shocks felt in the area over many months. Other sensible earth-movements occurred in connection with the Taupo earthquake series of 1922,^* the Amuri earthquake of 1888,^† the Wellington earthquake of 1855,^‡ and probably the Awatere earthquake of 1848.^§ There is also definite evidence of geologically-recent differential movement of earth-blocks at several widely separated points in both Islands.

A comparison between the records of destructive earthquakes in New Zealand and similar records in other seismic countries shows that the seismicity of New Zealand in general is surprisingly high. This, however, is due to the occurrence of a large number of earthquakes of the semi-destructive type, with comparatively few of the disastrous type.

During the period 1835–1934 sixty-nine destructive earthquakes are known to have occurred in New Zealand, forty-nine of which were of the semi-destructive-type (not exceeding intensity R.-F. 8). There were fourteen of intensity 9, and six of intensity 10.^*

* P. G. MORGAN: N.Z. Geological Survey; Animal Report for the year 1923, p. 10.

† ALEXANDER MCKAY: Reports of Geological Explorations during 1888–80. Wellington, 1890.

‡New Zealand Government Gazelle, Wellington, Vol. 2, No. 14, 17th October, 1855, p. 116. Sir CHARLES LYELL, “The Principles of Geology?” tenth edition, 1868, Vol. 2, p. 82. London: John Murray.

§ New Zealand Government Gazette. Wellington, Vol. 1, No. 27, 13th November, 18–18, and Vol. 1, No. 20, 20th November, 1848. 11. S. CHAPMAN in Westminster Review, Vol. 51,1849.

The distribution of earthquakes throughout New Zealand itself during the period 1848–1934 shows that the region of intense seismic activity, where earthquakes are frequent and occasionally severe, includes the eastern and southern parts of the North Island and the northern part of the South Island.^†.

The Auckland Peninsula, South Canterbury, and Eastern Otago appear to have been comparatively free from earthquakes during the past hundred years. Although the seismic history of the Fiord region of the South Island is not very well known, there are records of sealers having experienced violent earthquakes in those parts in 1792, 1810, and 1826–27 ^‡ Also there is some record of violent earthquakes having occurred near Auckland in ] 834–35.^§

It is thus evident that, although some parts of New Zealand have experienced no severe earthquakes during the past hundred years, no assurance can he given that such will not occur there in the future.

The following table, compiled for some of the main centres in New Zealand, shows—(1) The mean annual frequency of all earthquakes during the period 1848–1934 ^† and (2) the number of destructive earthquakes during the period 1835–1934:^|—

Although there appears to be no regular annual variation in the frequency of New Zealand earthquakes, the mean monthly numbers over a long period indicate that earthquakes are on the average most frequent in March and least so in January. The mean monthly numbers follow approximately the mean annual variation of atmospheric pressure in New Zealand.^¶

During the period 1848–1935 the number of deaths recorded in New Zealand as due directly or indirectly to earthquakes was 284. Of these, 255 were due to the Hawke's Bay earthquake of 3rd February, 1931. A table giving details of the number of deaths due to earthquakes in New Zealand was published in the 1936 issue of the Year-Book.

* L. BASTINGS: “Destructive Earthquakes in New Zealand, 1835–1934,” N.Z. Jour. Sci. & Tech., Vol. 17, No. 1, July, 1035. Dominion Observatory Bulletin 103.

† L. BASTINGS and R. C. HAYES: “Earthquake Distribution in New Zealand, 1848–1934,” N.Z. Jour. Sci. & Tech., Vol. 16, No. 5, March, 1035. Dominion Observatory Bulletin 95.

‡ R MCNAB “Murihiku and (lie Southern islands” (1907). R, TAYLOR: “Te Ika a Maui,“ London, 1855.

§ Australasian Association for the Advancement of Science, Vol. 3, 1891, p. 531.

| R. C. HAYES: “The Seismicity of New Zealand Cities and Towns,” N.Z. Jour, of Sci. & Tech., 1936. Dominion Observatory Bulletin 111.

¶ R. C. HAYES: “Earthquake Frequency in New Zealand,” N.Z. Jour. Sci. & Tech., Vol. 10, No. 5, 1935. Dominion Observatory Bulletin 104.

No earthquakes of destructive force occurred in New Zealand during the year 1935. The maximum intensity reported was R.-F. 7, which occurred in an earthquake near Taupo on 15th July. The following table gives some particulars of the most important earthquakes in New Zealand during the year 1935. The table includes—(1) Earthquakes reported to have reached or exceeded an intensity of R.-F. 6; and (2) earthquakes which were felt over a wide area:—

During the year 1935 fifteen seismograph stations were operating in New-Zealand and the surrounding islands. Of these, eleven are directly under the control of the Dominion Observatory. The stations at Apia and Christchurch are controlled by the observatories at those places, whilst two stations are privately owned. In July a new station was established at Lake Monowai Power-house, where a Milne-Jaggar seismograph was installed. The Imamura seismograph at Takaka underwent extensive overhaul, and was out of action during the latter part of the year. The New Zealand subsidiary stations are operated by officers of various Government Departments, by the engineers of some of the Electric-power Boards, and by private individuals.

Since 1888 there has been established in New Zealand a system of observing local earthquakes, depending entirely on personal observations. At first this system was confined to selected telegraph-offices throughout the Dominion, but more recently a number of lighthouse-keepers have also taken up the work as well as many private observers. Special forms are supplied for reporting earthquakes, in which information is required concerning the observed time of the shock, the direction and the duration of the movement, and also general effects which are likely to lead to a determination of the intensity of the earthquake.

There are at present 110 of these non-instrumental reporting-stations distributed throughout the Dominion.

The following summary gives the number of earthquakes reported felt in New Zealand for each month during the year 1935, and also the maximum intensities:—

The next table gives the number of earthquakes in which the maximum intensity reported reached the various decrees of the Rossi-Forel scale:—

The total number of earthquakes reported felt, and the maximum intensities reported in each of the years 1921 to 1935 inclusive, are as follows:—