The hot springs of New Zealand

Preface

The object of this book is to bring before the notice of the medical profession the value of the mineral waters of New Zealand.

In New Zealand itself, and to a certain extent in Austraha, they are of course well known, and indeed it is probable that in no other country has a larger proportion of the population taken advantage of the presence in its midst of thermal springs.

Thus, although the population of New Zealand is only about a million, there were given, during the seventeen years in which the author was in charge, nearly two and a half million baths at Rotorua alone, although of course a certain proportion of the bathers were visitors from overseas.

The events of the last few years have brought home to all of us the necessit}^ for making the British Empire selfsupporting, and it is well that the available resources of that Empire should be made known as widely as possible amongst its members.

It is with no thought of belittling the springs and spas of the British Isles that the merits of those so far afield are thus brought forward.

No one more than the author, who himself practised for several years at an English spa, is more fully impressed with their value, but all of us must also admit their limitations.

The British Isles are deficient in certain waters, and for that reason great crowds of patients every year flocked to foreign spas. Many of these spas are now, and perhaps will be for many years to come, practically closed to British

VI

PREFACE visitors, and it behoves us to see whether within the confines of our own dominions we cannot fill the deficiency.

With the exception of purgative waters, the missing springs can certainly be supplied in New Zealand, and there are certain waters, such as the nascent sulphuric acid waters at Rotorua, which are of a potency and therapeutic value undreamed of in England, and which are wholly unrepresented in Europe.

The author, in pressing the merits of the New Zealand spas, makes no claim that they can compete on what may be termed social lines with those of the Old World, In the matter of theatres, music, indoor amusements, and so forth, they are woefully deficient ; but in his opinion, what they lack in this direction is more than counterbalanced by their other attractions.

Change of environment is one of the most potent weapons in our armamentarium ; and the change of scene from, say, an English town to the Thermal District of New Zealand with all its wealth of weird and wonderful sights, its beautiful lakes, rivers, mountains, asd forests, its geysers, boiling springs, and mud volcanoes, its Maori villages with their picturesque inhabitants, the cottages crazily and precariously perched on the brink of boiling destruction, the housewife washing clothes in a hot spring, or nonchalantly cooking the dinner in a steam-hole — all these things provide more change of scene than a mere trip to a cosmopolitan Continental spa.

For such shortcomings as the New Zealand spas may possess — and they are of course as numerous as elsewhere — the author must bear, at any rate in part, the blame. He was appointed in 1902 as Government Balneologist to advise in the development of the health resorts of New Zealand. Such a unique appointment carries with it corresponding responsibilities, and the author is keenly aware of his deficiencies. The wealth of material was so great, the choice so large, that it was a matter of extreme difiiculty to choose a policy. Rightly or wrongly, the line he advised was

PREFACE vil

to develop one spa, Rotorua, thoroughly, rather than attempt, with hmited means, to develop half a hundred ; and so the visitor may rest assured that at Rotorua, at any rate, he will find the balneological amenities to which he is accustomed nearer home.

Further, he will find, if he be so minded, an unwonted charm in the simplicity and naturalness of the lesser spas ; and if he be so unconventional as to venture to leave the tourist beaten track, and philosophic enough to put up with a few minor discomforts, his venturesomeness will not go unrewarded. Some of the author" s pleasantest recollections are of long excursions into the " back country," of a tent pitched before sunset and bedded with fern, and of a bath in a spring or a hot bubbling river under the stars, while the " billy " boiled for the evening meal.

There comes to all of us, unhappily, a time in which the illusions of youth are lost. The author labours under no illusions that a book such as this will be read through from beginning to end, save by the heroic few. The busy practitioner has so many and diverse calls, intellectual and physical, on his time, that it is contrary to all our experience of human nature to expect him to delve deeply into the intricacies of a subject in which he may be only remotely concerned, and he may well feel inclined to skip such chapters as those dealing with the principles underlying balneological treatment.

Should he, however, desire fuller information, and have no standard work on balneology at hand, these pages have been inserted, not without some diffidence, for his guidance.

In the tabulated analyses of mineral waters the results are compiled from the figures published by the Dominion Analyst, and are expressed as salts in grains per gallon. According to modern views this is not a strictly scientific method of expression, as it is now generally assumed that the various substances present in mineral water exist, in part at any rate, in the form of dissociated ions and not of actual salts.

Vlll

PREFACE

A result expressed in terms of ions is, however, unintelligible to any but the expert chemist, and would be of no practical guidance to the doctor — and practical utility is essentially the aim of this work.

Too much stress, however, should not be laid on the mere chemical composition of a water. The majority of the so-called rheumatic and allied diseases are now known to be toxaemias of bacterial origin, and a mineral water is used even more often for its physio-therapeutic than for its pharmacological properties. Balneology, in fact, marches hand in hand with bacteriology, and it would even appear as if, in the near future, in the treatment of many chronic diseases it will be regarded as an adjunct, though an invaluable adjunct, of that branch of science.

With the exception of the tables of analyses, however, the remainder of the work is original, and represents the author's personal experience and views, and, as an excursion into hitherto untrodden country, is published with the hope that it may be interesting as well as useful.

The first few chapters have been inserted largely for the benefit of the patient himself.

There can be very few intelligent visitors to the Thermal District who do not burn with curiosity to imderstand something of the why and wherefore of the wonderful thermal phenomena they see around them ; and so a brief, and, it is trusted, a comprehensible, account is given of the geological factors involved in the evolution of geysers, volcanoes, and other " sights."

Finally, the author acknowledges gratefully the kindness of the Government Meteorologist in contributing a chapter on the climate of New Zealand.

Arthur S. Herbert.

I Upper Phillimork Place, Kensington, W.

March 192 1.

Part I Descriptive Chapter

I. KOUTES AND GENERAL DESCRIPTION

II. HYDROTHERMAL PHENOMENA .

III. HOT SPRINGS ...

IV. GEYSERS AND BOILING MUD SPRINGS

PAGE

3 15 24 33

Part II • Balneological

V. THE MINERAL-WATER HEALTH RESORTS — SPAS

VI. THE SULPHUR SPAS

VII. THE ALKALINE SPAS

VIII. THE SALINE SPAS .

IX. THE CALCIUM SPAS

X. THE SIMPLE THERMAL SPAS

XI. CLASSIFICATION OF THE RHEUMATIC DISEASES

XII. SPAS SUITABLE FOR INDIVIDUAL CASES .

XIII. CLASSIFICATION AND ANALYSES OF THE MINERAL WATERS ....

XIV. THE CLIMATE OF NEW ZEALAND

ix

54 III

137 144

162 211

CONTENTS

Part III Balneological Principles Chapter

XV. SPA TREATMENT .....

XVI. MINERAL- WATER TREATMENT

XVII. ACCESSORY PHYSICAL TREATMENT .

XVIII. DIET .......

XIX. ENVIRONMENT — CLIMATE — SUGGESTION .

APPENDIX ......

INDEX ....

225 229

268 274

LIST OF ILLUSTRATIONS

FIG.

1. WAIROA GEYSER, WHAKAREWAREWA, ROTORUA

2. MAP SHOWING NEW ZEALAND IF PLACED IN CORRESPOND-

ING LATITUDE OF NORTHERN HEMISPHERE , page 5

3 MAP OF NORTH ISLAND, SHOWING THERMAL DISTRICT ,, 9 3A. MAP OF THERMAL DISTRICT . . . . .,13

4. DIAGRAMMATIC SECTION OF A VOLCANO . . ,, IQ

5. WAiMANGU IN ERUPTION .... facing Page 20

6. WAIMANGU IN ERUPTION . . . . ,, ,, 21

7. DIAGRAM OF THE FORMATION OF ACID MINERAL WATER page 30

8. A SMALL GEYSER, WHAKAREWAREWA . facing Page 33

9. A. FUMAROLE ON SLOPING SURFACE . 9, B. FUMAROLE ON A CLIFF- FACE 9, C. FUMAROLE ON GENTLY SLOPING SURFACE 9, D. FUMAROLE ON HORIZONTAL SURFACE

10. DIAGRAM OF THE GREAT GEYSER OF ICELAND

11. PAPAKURA GEYSER ..... facing page 38

12. A CLOSE VIEW OF THE MOUTH OF PAPAKURA GEYSER

13. A GEYSER OPENING THROUGH A POOL OF BOILING WATER

14. ANOTHER VIEW OF THE SAME GEYSER . „ ,. 38

15. THE MOUTH OF AN EXTINCT GEYSER . ,, , 38

xi page

> J xu

LIST OF ILLUSTRATIONS

FIG.

19. 20. 21. 22.

23- 24.

26. 27. 28. 29.

31- 32.

33- 34- 35-

36. 37-

THE " BRAIN-POT," WHAKAREWAREWA DIAGRAM OF GEYSER DRY-MOUTHED GEYSER .

., 42

BOILING SPRING ON BANKS OF WAIKATO RIVER . ., 43

DIAGRAMMATIC SECTION OF CONE OF GEYSER . ,,44

A CHAMPAGNE POOL

THE MALFROY GEYSERS, ROTORUA

WAIROA GEYSER, WHAKAREWAREWA

CONE OF WAIKITE GEYSER

A SILICA TERRACE .

SILICATED TWIGS AND LEAVES .

FLOOR OF A SILICEOUS POOL .

MUD VOLCANO IN ACTIVE ERUPTION

A BOILING MUD POOL

A BOILING MUD POOL

SURFACE OF A " PORRIDGE-POT "

" THE INFERNO." TIKITERE

CONES OF MINIATURE MUD VOLCANOES

A STUDY OF MINIATURE MUD-VOLCANO CONES ,,

THE SAME CONE AS IN FIG. 28, IN A QUIESCENT STAGE

.. 44

.- 44

.. 44

.. 45

48 48 48 48 48

HINEMOA S BATH A GIANT AZALEA FLY-FISHING AT OKERE

39. WAR CANOE .

40. THE MAIN BATHS, ROTORUA

.. 61

page 61 facing page 62

LIST OF ILLUSTRATIONS

Xlll

45- 46.

47- 48.

59- 60.

THE BATHS, ROTORUA .... facing

OHINEMUTU . .....

MAORI WOMAN COOKING IN A STE A:\I-H0LE

A NATURAL KITCHEN RANGE

A HOT " LAKE," OHINEMUTU

A MAORI MOTHER AND CHILD

A MAORI LAUNDRY .

WEAVING A FLAX MAT

HONGI, A MAORI GREETING

A POI DANCE .

A FIGURE OF THE POI DANCE

ANOTHER FIGURE OF THE POI DANCE

A HAKA .....

A FIGURE IN THE HAKA .

ANOTHER FIGURE IN THE HAKA

EXAMPLE OF MAORI WOOD-CARVING

PANORAMA OF HANMER PLAINS.

A BATH-HOUSE, HANMER .

QUEEN MARY's HOSPITAL, HANMER

MUD VOLCANO, WAI-O-TAPU

THE " devil's bridge," WAI-0-TAPU

THE " ECHO LAKE," WAI-O-TAPU

NATURAL WARM SWIMMING-BATH, WAIRAKEI

THE WARM SWIMMING-BATH, WAIRAKEI

THE " GREAT GEYSER," WAIRAKEI .

THE " dragon's MOUTH " GEYSER, WAIRAKEI page 62 64

64 64 64 64

93 96

100 100 100

103 103 103

XIV

LIST OF ILLUSTRATIONS

FIG.

facing page io_;

pagi

C7. OUTFLOW FROM THE GREAT GEYSER ^)8. KERAPITI BLOW-HOLE

69. THE HUKA FALLS .

70. ARATLVTL\ RAPIDS .

71. THE "twins" geyser, WAIRAKEI

72. MOUTH OF THE " TWINS " GEYSER

73. " eagle's NEST " GEYSER W MRAKEI

74. " crow's NEST " t.LVSLK. TAUPO

75. A BOILING SPRING, TAUPO

76. THE DINING-HALL, THE SPA, TAUPO

77. THE BATHS, TE AROHA .

78. THE BOWLING GREEN, TE AROHA

79. A GROVE OF NIKAU PALM AT MORERE

80. THE BATH-HOUSE, MORERE

81. LIMESTONE ROCKS, KAMO

82. THE HANDS IN RHEUMATOID ARTHRITIS

83. X-RAY OF HAND IN RHEUMATOID ARTHRITIS

84. SPUR FROM THE OS CALCIS

85. DIAGRAM OF X-RAY PICTURES

86. TOPHACEOUS MASSES IN THE HAND OF A MAORI page lacing page

■ page facing page

• page facing page

105 106

PART I DESCRIPTIVE < p

D

Chapter I Routes And General Description

Comparison with the British Isles. — New Zealand has been termed the " Britain of the South." The description for once in a way is really apt, for while, as a general rule, one is prone, and justly prone, to mistrust the facile labels which are nowadays so freely distributed, in this case the name is fully justified.

Of course, in dealing with the southern hemisphere, there is a necessary inversion of northern ideas and terms ; the South is cold and the North is hot, and Christmas falls at midsummer. Allowing, however, for this inversion, it is curious how closely parallel are these two Britains of the North and South.

Lying in the Southern Ocean, almost exactly antipodean to Britain, New Zealand also consists of two main islands, though in this case they lie end to end and north and south, instead of side by side and east and west. •

The Scotch mountains of the north are represented, and eclipsed, by the Southern Alps ; the lochs of the western highlands have their counterpart, though on a grander scale, in the fiords and sounds of the South Island ; and the southern extremity of the country is very largely Scotch. The cold north-east wind of Britain is, for much of New Zealand, represented by the south-west, and the north-east wind brings rain and warmth.

It is of course easy to pursue analogy farther than is profitable. Every country and every community has special individualities which mark it out as a thing apart, and without such characteristics the world would be robbed

4 THE HOT SPRINGS OF NE\\' ZEALAND

of half its charm. It is the pride of New Zealand that, while she is, of all the daughter nations, the one most nearly like the mother country, she is yet most unmistakably stamped with her own individuality, is a young, vigorous, and original nation and no mere copy.

Climate.' — Although lying much nearer to the equator, roughly between lat. 34° and 47° S., than do the British Isles, which lie between lat. 50° and 59° N., the climate of the two countries is by no means so dissimilar as these figures would indicate. For while Britain is warmed by the Gulf Stream, New Zealand is kept more temperate by the enormous surrounding areas of the southern oceans. Thus New Zealand corresponds in latitude to Italy in the northern hemisphere (vide fig. 2) ; but to get an approximately equal climate, one would have to imagine Italy an island shifted, say, five hundred miles north-west of the coast of Portugal. As compared with the British Isles there is in New Zealand more sunshine, and warmer sunshine ; less mist and fog, and fewer grey days ; a slightly heavier rainfall, with fewer rainy days ; perhaps, if anything, rather more wind. There is, however, much less contrast between summer and winter. The summer climate of New Zealand is somewhat warmer, and in this there is much less difference between the North and South Islands than might be anticipated, while the winter climate is, except on the inland highlands of the South Island, distinctly milder than that of the south of England. In a word, the climate is more equable, more sunny, and somewhat warmer.

It is the climate of England at its best, " only a little more so."

The contrast of the changing seasons is also minimized by the character of the vegetation. With few exceptions the native trees and shrubs are evergreen, and it is only in those increasing areas planted with deciduous European

1 For a fuller and more technical account of the climate the reader is referred to pages 211-221, which have been kindly contributed by the Government Meteorologist, the Rev. D. L. Bates.

BERLIN

-.. iSt^cart I

VIE.NNA

TRIA

CcQoa

CHRI^-j;

:hurc

'^euii

^ao

V;

M £

A^K Cap*

-Wana f . Chtmer

-Scale of English miles: ■"''I

Fig. 2.— map SHOWING NEW ZEALAND AS IT WOULD BE SITUATED IF PLACED IN CORRESPONDING LATITUDE OF NORTHERN HEMISPHERE, BUT WITH EAST, INSTEAD OF WEST, LONGITUDE.

ROUTES AND GENERAL DESCRIPTION 7

trees that the bare boughs bring home to one the fact of winter.

In the matter of elevation the principal spas are fortunately placed, and allow a good deal of choice. Thus, in the North Island, Te Aroha, Waiwera, Helensville, and several others are at or near the sea-level ; the " thermal district," including Rotorua, Wairakei, and Taupo, is on an elevated inland plateau a thousand feet or so above sea-level ; Hanmer, in the South Island, is somewhat higher, and in bracing mountainous country.

As purely mountainous resorts there are " The Hermitage " at Mount Cook, at an altitude of 2.500 feet, with easy access to mountain huts higher up, and an accommodation house high up on Mount Egmont, near New Plymouth.

Bracing resorts at medium altitude are Queenstown, on Lake Wakatipu, and the small towns on the upland plateau of Central Otago.

Ocean Routes. — It must be confessed that New Zealand hes " a long way from anywhere." From Australia it means about four days' passage from Sydney to Auckland or from Melbourne to Wellington, while from England it means a minimum of from four to six weeks, whatever route be taken.

While, however, this great distance presents many drawbacks, especially to the tourist with limited time at his disposal, to the invalid not too hampered by such considerations the long voyage is, in many cases, a distinct advantage.

Thus in cases of chronic disease — and it is of course for chronic diseases that spa treatment is especially indicated — the prolonged enforced rest, the abundant fresh air and sunshine, and the novel surroundings of an ocean voyage are very material aids to recuperation, and form an excellent preliminary to a course at a spa and an equally excellent " after cure."

There is also considerable choice of routes, so that a traveller need not be bored by retracing his steps on his homeward journey. Again, a route can be chosen to suit

8 THE PIOT SPRINGS OF NEW ZEALAND

the special needs of an invalid. Thus, if it be desirable that he should get plenty of change of scene and interest, he should be sent via the Mediterranean, calling at French and Itahan ports, the Suez Canal, Colombo, and Austraha. In Australia he wiU probably get a day or two at Perth, Adelaide, and Melbourne, before disembarking at Sydney for Auckland. He can return by an alternative route via Vancouver and across Canada, or by the Panama Canal. Should the Suez route be chosen, care should be taken, in the case of delicate patients, to avoid the summer months in the Red Sea ; but as, under ordinary conditions, he would be leaving England in autumn to catch the New Zealand summer, any excessive heat is not likely to be encountered there, and it is not until he gets to Ceylon that he encounters much in the way of tropical conditions. Australia will, of course, be reached in the early summer, but if he times liis journey to arrive about November he will probably find the climate delightful.

Should, on the other hand, it be desirable to rest the patient as much as possible, to avoid the fatigue and excitements of landing at ports, and to avoid prolonged heat, he should be sent via the Cape. By this route he will probably touch at Teneriffe, Cape Town, and Hobart, and on his return journey can go round Cape Horn, only calling at a South American port ; and the passage through the tropics, both in going out and coming home, will be comparatively short.

The choice of routes will depend, then, partly on climatic requirements and partly on the idiosyncrasy of the patient. If he is liable to be bored by the monotony of a long sea voyage and few ports, he had better avoid the Cape route, and perhaps Panama.

Clothing. — The invalid, by leaving England in the autumn, will be getting three summers running, and he will necessarily spend several weeks under tropical conditions. A tropical outfit for board- ship will therefore certainly be needed, but he will be well advised to wear very thin white flannel

C.Maria Van Diemen\ i North C.

NORTH ISLAND^

« i\Great Barrier I,

East C.

SOUTH ISLAND

MAP SHOWING HOT SPRINGS AREA till 1 1 1 1 1 II

Railways

Tourist Coach Roads

Thermal District y//////7/m^/V//fy/,

Places with Hot Springs underlined

Tic. ,.— MAP OF NORTH ISLAND, SHOWING THERMAL DISTRICT AND MAIN

HOT SPRINGS CENTRES.

ROUTES AND GENERAL DESCRIPTION 11

rather than white duck. In New Zealand he will find that what suited him for an English summer will suit him for a New Zealand one. Visitors from Australia need hardly be reminded how much cooler the New Zealand summer is than their own.

Access on Landing. — A glance at the accompanying map (fig. 3) will show that the spas of New Zealand are, with the exception of Hanmer, confined to the North Island. While there are numerous places marked as mineral springs, and still more numerous springs unnamed, the average overseas invalid will probably be making either for Rotorua or Te Aroha, while the tourist will surely find himself sooner or later in the Thermal District.

In the vast majority of cases travellers will be disembarked at either Auckland or Wellington. The journey from Auckland to Rotorua is only 170 miles by train, while from Wellington it means a long and tedious journey. There is, however, a sleeping-car on the train. Te Aroha is reached by a branch from the Rotorua line.

Thermal District. — The thermal district covers a very extensive area (vide map 3.^). Its limits are of course somewhat difficult to define, and indeed there are large numbers of hot springs far outside its uttermost boundaries, but as a matter of convenience it is held to include the zone of volcanic springs ranging from the central volcanoes south of Taupo in a northerly and north-easterly direction to White Island and Whale Island in the Bay of Plenty. The main geographical features of this district are that it is an elevated pumice plateau, 1,000 to 1,500 feet above sea-level, dotted with numerous large lakes and with isolated extinct volcanic cones, and culminating in the very centre of the North Island in a group of active, extinct, and semi-extinct volcanoes. Of these mountains, snow-clad Ruapehu (9,175 feet), a volcano extinct but for its hot springs, is the highest point in the island and dominates its sister mountains Ngauruhoe (7,515 feet), a still active volcano, and Tongariro (6,400 feet).

At their feet lies Taupo Moana/ a lake some twenty miles or more in length and nearly as much in breadth. This lake, largely fed by the melting snows of the mountains, overflows by the great Waikato River to the sea, and on its shores, at Tokaanu and Taupo, and on those of the upper reaches of the river and its tributaries, as at Wairakei, Wai-o-tapu, and Orakei Korako, may be found innumerable boiling springs, fumaroles, mud volcanoes, and other evidences of hydrothermal activity.

Towards the northern edge of the plateau, and beyond the watershed of the Waikato, will be noticed a chain of numerous lakes, Rotorua,- Roto-iti, Roto-ehu, Roto-ma, Tarawera, Roto-mahana, and many others, grouped around numerous extinct volcanic peaks, while the two last named are at the foot of Tarawera Mountain, which, while now quiescent, was in active eruption in 1886.

Here we find, in addition to numerous isolated springs, two main groups of hot springs, one centred at Rotorua and the other at Rotomahana, and reaching its climax there at the great Waimangu geyser.

The whole of this district is the happy hunting-ground of tourists in quest of wondrous thermal " sights " and of sport, or of invalids in search of health. For both, the centre of the district is Rotorua, for here the railway ends, and here are, besides geysers and hydrothermal sights, baths and all the resources of a modern spa. From here starts the main line of tourist traffic to Waimangu, Wai-otapu, Wairakei, and Taupo, and the overland route thence to the Wanganui River on the main trunk line.

1 Moana — the sea, ocean, — pron. mo-ahna.

2 Roto — lake.

Ftg. 3a.— map of THER>L\L DISTRICT, SHOWING MAIN TOURIST ROUTES.

Chapter II Hydrothermal Phenomena

No one visiting the " Thermal District " of New Zealand can fail to be impressed by the magnitude and variety of the hydrothermal phenomena. On every side one sees hot springs of every size, shape, temperature, and colour. Here a spring is blue and boiling furiously, there a comparatively placid pool may be bright green or perchance a mustard yellow.

Closer investigation will show as great variations of chemical composition, not only in waters of obviously different appearance, but in waters apparently identical. The most casual tourist is interested in the question — " why ? " much more so the invalid, who is looking to these same waters to rid him of his malady ; and it is felt that a chapter dealing with these phenomena, and, as far as possible, explaining them, can hardly fail to be of general interest.

There are certain phases of the question which can only be explained tentatively, and certain subtle differences of working and appearance which we can hardly explain at all; but on the whole, all the major phenomena can be elucidated on general geological principles, after careful investigation of local conditions.

Fumarole the prototype of all hydrothermal activity. — It will be the purpose of the following pages to attempt to explain how all the protean hydrothermal activities of the district are but children of the parent fumarole or " blow-hole," and that hot springs, geysers, boiling mud springs, silica terraces, and probably even volcanoes, all have as their primary agent a jet of steam blown out of the earth's hot interior.

To obtain a clear idea of hydrothermal phenomena it is necessary to consider briefly a few elementary facts in geology ; and as all the hot springs of the district are of volcanic origin, it will repay us to digress for a time and consider in some detail the structure and modus operandi of a volcano. If some of the statements made here may seem somewhat elementary or somewhat dogmatic, it must be remembered that this book is written essentially for the lay reader and not for the geologist.

We must conceive, then, the earth as being composed of a white-hot mass, whose exterior has cooled to a relatively thin, hard crust, and whose interior, the magma, so far from being a molten liquid, is maintained in a solid condition by enormous pressure. It is possible, and even probable, that much of this central mass may consist of superheated gas, but so modified by pressure that it has the physical consistency of a solid.

Somewhere in this hot mass has been heated the water which is the basis of our hot springs and geysers, and which is by most geologists conceived to be the basis of all volcanic action.' There are two rival theories as to the origin of this water : it may have come in recent times by percolation from the surface, from leakv river, lake, and ocean beds, and from rain penetrating the soil, or it may have arisen from primeval water imprisoned in the magTna through the ages. In the former case it is assumed that it only penetrated the hot crust, that it was heated by

^Brun {Recherches sur I'exhalaison volcanique) would rather appear to have upset the orthodox theory by his researches. He showed that when " active " unoxidized volcanic rocks are heated to a certain temperature, gas and volatile salts are given off with explosive violence (i kilo of Krakatoa obsidian yielding 1,577 <^C- of gas at 800° C). and to this action he attributes volcanic outbursts and the formation of pumice. He points out that water vapour is largely dissipated at 150° C. and wholly so at 300° C. While he asserts that volcanic explosive eruptions are anhydrous, he maintains that solfatara and fumaroles owe their aqueous character to the invasion of partially cooled volcanic rocks by superficial waters.

HYDROTHERMAL PHENOMENA 17

the rocks and probably never reached the white-hot interior.

It might be thought that the enormous pressure of rising gases and steam would preclude the passage of water beyond a limited depth, but it has been shown pretty conclusively that water can penetrate rocks by capillary attraction against the most enormous forces of heat and pressure.

In favour of this theory of origin is the fact that volcanoes are almost invariably found near the sea or a large lake, and again, in New Zealand at any rate, the hot springs and geysers are almost always close to a river or lake bed, or the sea-shore.

The other theory, that of the primeval "original" water imprisoned in the magma, has at least as many supporters and makes a powerful appeal to the imagination.

According to this theory, before the formation of the earth's crust it was surrounded by a dense atmosphere of steam and gases, the former representing the present waters before their condensation. Much of this steam was absorbed by the molten magma, and has escaped slowly ever since. In what form it is imprisoned is perhaps a matter for conjecture. Under increased pressure of course the boiling-point of water rises, but the process does not go on indefinitely. The critical temperature of water is 773° F., and as the temperature of the magma near the surface is about 1,500° F., and is much more at greater depths, such imprisoned water vapour must be white-hot, and probably exists in a state of " dissociation," and we can only term it indefinitely " water substance." A substance that by reason of pressure and temperature is a white-hot solidified potentially explosive gas is hard to reconcile with our ideas of water !