THE NEW ZEALAND OFFICIAL YEAR-BOOK, 1934

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 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 undercurrent 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 now Blue Bath are now completed, and afford one of the most attractive playgrounds for visitors to Rotorua. 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 20 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. The Blue Bath, with all its comfortable and attractive appointments, is one of the finest swimming-baths in the Southern Hemisphere.

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 Czechoslovakia, 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 hyperæmia 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, 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 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. 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 8.4° 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 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 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 Palæozoic 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 largo 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 Archæan age, resembles the part of the Ordovician strata of western Nelson that has been similarly invaded and metamorphosed and may well be of early Palæozoic age. Different authorities assign the mica, chlorite, and quartz schists of Central Otago to ages that range from the Archæan to the Triassic. They are certainly Palæozoic or older, since they grade upward into greywackes that, at Clinton, contain Permian fossils.

Sliurian rocks are certainly known only in the Baton and Wangapeka districts, and Devonian rocks at Wangapeka and Reefton. These beds, fossils from which have lately been examined in England, cover only small areas. But the old Geological Survey mapped wide tracts of country in Nelson and Otago, covered with beds of the To 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 Bay, 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 Bay, 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, where Oligocene beds are altogether absent. In north Taranaki, the Murchison basin, and parts of the West Coast, thick coal-measures of this age contain workable seams 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 to-day 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 lowlands generally were formed or profoundly modified during this period, and the soils that cover thorn 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 Palæozoic 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 Palæozoic 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 Palæozoic 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 Coromandel, 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 duo 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.”

After several years of intense seismic activity, the close of the year 1932 witnessed a return to less active conditions. The most important earthquake during the year occurred on the 16th September at 1.25 a.m., when the districts between Gisborne and Wairoa were severely shaken. Considerable damage was done to buildings in the towns mentioned, and parts of the country to the north and east of Wairoa were very disturbed. Fortunately, no serious injuries resulted from this earthquake. In the vicinity of Wairoa and to the northward the intensity reached 9 on the Rossi-Forel scale. The shock was felt with decreasing intensity over the whole North Island, except the Auckland Peninsula. - The epicentre did not coincide with the area of greatest surface damage, but was located beneath the sea, about twenty miles east of the Mahia Peninsula. The adopted geographical position of the epicentre is given below, in a summary of the most notable earthquakes in 1932.

During 1932 new seismological stations were established at Chatham Islands, Tuai, Bunnythorpe, and Greymouth, bringing the total number of New Zealand stations up to thirteen. By the courtesy of the Government of Fiji, the records from the Suva seismograph are forwarded to the Dominion Observatory, Wellington, for measurement. With the exception of the observatories at Wellington and Christchurch, some of the New Zealand stations are operated by officers of other Government departments, and others by private individuals. Three of the stations are privately owned, the observers supplying records and reports, thus assisting in the general seismological work. A set of Wiechert seismographs with mechanical registration is installed at Apia Observatory, Western Samoa.

The Dominion Observatory, Wellington, and the Magnetic Observatory, Christ. church, publish preliminary earthquake reports each month, giving data regarding the principal earthquakes recorded. More complete reports are also published from time to time. These reports are sent to the General Secretary of the Seismologicall Committee of the British Association, to the Station Centrale Sismologique, Strasbourg. France; and to the principal observatories of the world.

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-officers 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.

The following summary includes all earthquakes reported felt in New Zealand in 1932:—

The next table gives the number of earthquakes in the year 1932, in which the maximum intensity as reported reached the various degrees of the Rossi-Forel scale.

The maximum intensity experienced in each of the years from 1921 to 1932 (inclusive) was as follows:—

During the year 1932 no deaths resulted from earthquakes in New Zealand. The number of deaths due to earthquakes at present totals 275; 251 of which were due to the Hawke's Bay earthquake of 3rd February, 1931.

For details regarding deaths due to earthquakes in New Zealand the reader is referred to the Official Year-Book for 1933.

The New Zealand Meteorological Office is located at Wellington. Weather forecasts, based on observations at 9 a.m. and 4 p.m., are issued at noon and 5 p.m. respectively. The midday forecast is telegraphed to approximately one hundred country centres, where it is displayed at the post-offices. The evening forecast is broadcasted from the New Zealand Broadcasting Board's stations at Auckland, Wellington, Christchurch, and Dunedin at 7 p.m. and 9 p.m. The 7 p.m. issue from Wellington includes weather reports from a series of stations as well distributed as possible over the Dominion and the surrounding area.

Rainfall data from approximately four hundred stations are printed monthly in the Government Gazette. Observations of temperature, pressure, sunshine, wind, &c., from about forty-five stations are published annually by the Meteorological Office. Papers on various aspects of the climate and weather of the Dominion are published from time to time in the Journal of Science and Technology as “Meteorological Office Notes.”

New Zealand lies wholly within the Temperate Zone, and, though they are stronger and more persistent farther southward, it is also wholly and at all seasons within the zone of prevailing westerly winds. Owing to its isolation and its narrowness in the direction of the prevailing winds, its climate is predominantly marine in character. Nevertheless, the modifications due to the height and continuity of the main ranges and the general high relief of the country are quite considerable, especially in the South Island. There is, for example, a very great variation in the rainfall from the western to the eastern side of the Southern Alps, and for so narrow a country features of a continental type are rather strongly developed in the interior of the South Island. By breaking up the prevailing winds and causing the air at different levels to mix, mountains tend, also, to prevent the stratification of the air into layers of different density. Consequently very extensive and persistent cloud-sheets are seldom experienced. New Zealand therefore enjoys a high percentage of sunshine, a factor of great importance in the climate of a country with so high a rainfall.

The principal current in the surrounding ocean waters is from south-west to north-east. Off the west coast of the South Island, however, the current divides, one branch turning southwards to Foveaux Strait, while others pass through Cook Strait and round the northern extremity of the Dominion. The rather small range in climate from north to south is probably accounted for by this current.

According to the widely accepted classification of climates developed by W. Köppen, New Zealand has the climatic formula Cfb, denoting a cool-temperate moist climate without marked seasonal variations in temperature or precipitation. Under the same formula are classified southern Victoria and Tasmania and parts of southern Chile in the Southern Hemisphere, much of Europe, Japan and Korea, and a strip of the west coast of North America in the Northern Hemisphere. Generally, however, it is a climate characteristic of the ocean rather than the land areas of the Temperate Zone.

Of all the climatic elements, probably the one that exerts the greatest influence on our lives is rainfall. It causes us much personal discomfort, but the production of the food by which we live depends directly on the availability of moisture from this source.

Its control by topography is very conspicuous. Areas exposed to the westerly winds have heavier rains than those protected from them by mountain ranges. Next, the greater the altitude, the greater in general is the precipitation. There must be a limit, beyond which precipitation begins to decrease again with altitude, but this has not yet been determined in New Zealand. The indications are that precipitation is heaviest between 3,000 ft. and 4,000 ft. The annual total varies from about 13 in. at Galloway in Central Otago to over 200 in. in parts of the Southern Alps.

The distribution of the precipitation throughout the year is little less important than its total amount, the effect of rainfall in winter, for example, being very different from that in summer. There are three principal factors controlling the annual variation of rainfall in New Zealand. The first of these is the proximity to the high-pressure belt in the subtropics. In this belt the rainfall year is divided into a dry summer and a wet winter season. We will call this distribution type A. As the distance from the high-pressure belt increases, the contrast between summer and winter decreases, so that by the time southern New Zealand is reached the variation due to this factor is small. The next most important factor is the influence of the prevailing westerly winds. These bring rains to the areas exposed to them, while those which are protected from them by mountain ranges have little rain when the westerlies are blowing. Now, the westerly winds are strongest in spring, the maximum flow being in October. There is a temporary drop in February, followed by a partial recovery in the autumn, but the flow is least in winter. The regimé of the westerly winds, therefore, tends to produce a second type of annual variation, type C, in which the rainfall is heaviest in spring, falls somewhat in the late summer, increases again in the autumn, and falls to a minimum in winter.

The third factor is the convection which takes place during periods of light winds, clear skies, and intense sunshine, especially when the preceding winds have brought cold air over the land from the South. After conditions of the type mentioned have endured for several days, the convection is likely to be so intense as to produce local showers. These are often heavy, sometimes accompanied by thunder, and occasionally of the nature of local cloud-bursts. Rainfall of this type is most common in the interior of continents. Being caused by solar radiation, it is most frequent when solar radiation is strongest—namely, in summer. According to type B, therefore, we would have a relatively wet summer and a dry winter.

Temperature is no less important than rainfall in determining the living conditions of a country and the yield from its soil. But it is much less variable, and in the Southern Hemisphere especially is largely determined by latitude. Its influence is therefore taken much more for granted. The specification of the temperature of a place is, however, not so simple a matter as might appear. Many different factors are involved in the determination of the precise temperatures experienced in any locality. The sea, for instance, responds very slowly to both daily and yearly changes in the amount of heat received from the sun, while on the land the response is rapid. Consequently, the nearer a station is to the sea the smaller are its daily and yearly fluctuations of temperature. It is to this effect that the principal difference between a continental and a marine climate is clue. Although New Zealand is narrow, the high ranges shield the country to the east of them to a considerable extent, so that there is a nearer approach to continental conditions than would otherwise be expected, particularly in the interior of Canterbury and Otago. Again, on plain country the air tends to stagnate, especially at night. At night-time the surface layer cools rapidly through radiation from the ground, while during the day it becomes heated by the sun. There is less stagnation in the warm layer of the daytime than in the cold layer of the night. Consequently, stations on level plains or plateaux tend to be subject to frost and to have a relatively low mean temperature. The effect is accentuated near the slopes of hills because the cold air flows away down the slopes to lower levels. The hills, therefore, gain freedom from frost at the expense of the plains. In windy situations, also, the susceptibility to frost is lowered owing to the prevention of stagnation. Apart from the effects due to air-drainage and windiness, the temperature decreases with altitude. In temperate latitudes the fall is about 9° F. per kilometre. It is unsound, therefore, to compare, for example, temperatures recorded at Thorndon, Wellington, which was only 12 ft. above sea-level, with those at the present meteorological station at Kelburn, which is at an altitude of 415 ft., without making allowance for this difference in altitude. Such a procedure would lead to the erroneous conclusion that the climate had become colder. If charts of mean temperature are to be prepared it is clear that they will be very complicated, especially in a mountainous country like New Zealand, owing to this effect of altitude. It is usual, therefore, to simplify matters by applying a correction at the rate of 9° F. per kilometre or approximately 2°.7 F. per 1,000 ft. This has been done in Table 3. The Rotorua values, for example, have been increased by 2°.5 F., the station being 925 ft. above sea-level. If the actual temperature is required, it can be found by reversing this process.

In New Zealand publications it has been the general practice to derive monthly mean temperatures from the means of the daily maximum and minimum. But, even on the average, the mean of the maximum and minimum differs slightly from the true mean for the day. The correction to the mean for the day has been determined from the records of thermographs with fair accuracy at Wellington and more roughly at several other places.

In Table 3, therefore, the temperatures are reduced to sea-level and mean of day. For the remainder of the temperature tables the observed readings have been used without correction. All are in Fahrenheit degrees.