[LIBRARY I UNIVERSITY OF I CALIFORNIA SAN DIEGO J WATER ITS ORIGIN AND USE WAT E R ITS ORIGIN AND USE BY WILLIAM COLES-FINCH RESIDENT ENGINEER TO THE BROMPTON, CHATHAM, GILLINGHAM, AND ROCHESTER WATER COMPANY, KENT Illustrations of Mountain and Glacier Scenery from the original pictures of MRS AUBREY LE BLOND (MRS MAIN) "The lapse of time which is herein indicated, fills the mind of man with awe ; but nature has no need to consider time ; has she not eternity to work in?"- LORD AVEBURY. LONDON: ALSTON RIVERS, LTD. BROOKE STREET, HOLBORN BARS, E.G. 1908 PREFACE BEING professionally interested in the finding and distri- bution of water, as engineer to an important waterworks, I have naturally been led to give this subject some atten- tion and study, and I have derived no little pleasure in gathering together into the present volume the notes and memoranda which I have accumulated during a number of years, in the hope that my readers may find in it some matter of interest, and may be led to, the contemplation of the wonders of nature. Water in its various forms has been dealt with by some of the most eminent of scientists. The subject, like the boundless ocean, is so wide, that there are few branches of scientific research in which it does not claim attention. This book, however, does not pretend to be a scientific record ; it is simply an ordinary person's interpretation of what he sees in nature, and represents his best efforts to describe the same. Of such sources of information as were at my disposal, I have made free use : originality on such a theme was not contemplated, nor is it possible. It is a truism that we know least about the common things we see and use every day of our lives. There are vi PREFACE writers on such subjects who have the happy gift of imparting useful information in a pleasant and agreeable way. In such company I have added to my slender store of knowledge of the marvels of nature, and have derived from their works much profitable amusement ; so I set out to write down in simple language, and in proper sequence, the results of my recreative studies and personal experiences. That others may be encouraged to a greater curiosity about such things, and find therein both greater interest and reverence for the Great Author of all, is the purpose of this story. With this special object in view, I have freely intro- duced verses bearing upon the various subjects ; and I hope that these may help to awaken the interest of those who are not generally attracted to such subjects as this work treats of, and in this manner may make the scientific facts mentioned appear in a more acceptable form, for poetry and nature are ever closely allied. Many of the scientific facts mentioned in this book are recorded in various works of note, but they have never before been brought together in this manner. Where I have quoted verbatim from any writer, I have endeavoured faithfully to mention the fact. Should I have omitted to do this in any instance, I trust that the author will generously regard it as an oversight, and accept this as my apology. In making this request I am but copying one of the minor poets of the last century, Peter Coxe, who in 1825 brought out a poem which he had "strengthened" con- PREFACE vii siderably by quotations from poets greater than himself. " Distinguishing," says Joseph Bennet, " the larger extracts in the usual way, he left the smaller to the unaided perceptiveness of his subscribers ; but, fearing the critics, he indited an apology, which concluded : " ' When we with proper caution weigh, And stealing, meditate our prey ; And this we state lest any look For plagiary to spurn the book, And cautious mention at the starting To bar all quarrel at the parting.' " I wish to express my thanks to Mrs Aubrey Le Blond for the beautiful Alpine illustrations which adorn this volume, and to my friend Mr R. Keith Johnston for the help he has given me in revising the manuscript and in seeing my book through the Press ; also to Mr George F. Deacon, for his kind assistance in connection with the illustrations of the Vyrnwy Dam. Should those who read my book derive as much pleasure and profit from its perusal as I have found in its compila- tion, the time and labour given to it will find sufficient compensation, and I shall be amply rewarded. W. COLES-FINCH. WATERWORKS HOUSE, LUTON, CHATHAM, KENT, June 1908. CONTENTS CHAPTER I HEAT PAGE In the Beginning ...... 1 Solar Heat ....... 8 Solar Constant of Heat . . . . . .13 Distribution of Heat . . . . . .15 Effect of Heat on Land, etc. . . . . .16 Thermal Unit of Heat . . . . . .17 Heat of Combustion of Various Fuels . . . .18 Temperature . . . . . . .18 Earth's Internal Heat ...... 20 CHAPTER II ATMOSPHERE Atmosphere ....... 24 Atmosphere, Composition of . . . .27 Atmosphere, Analysis of ..... 29 Specific Gravity of Elastic Fluids . . . .29 Carbonic Acid in Atmosphere ..... 30 Evaporation ....... 31 Vapour ........ 35 Vapour, Weight of . . . . .36 Saturation of Air ...... 38 Condensation of Vapour ..... 39 Vapour and its Effects ...... 39 Temperature of Atmosphere ..... 42 Compression of Atmosphere ..... 46 Expansion of Air ...... 48 Height of Atmosphere . . . . . . , 50 Height Penetrated ...... 51 CONTENTS PAGE , . 53 Pressure of Atmosphere Contamination and Purification of Atmosphere Velocity and Impulse . 63 Stellar Space CHAPTER III CLOUDS 66 Clouds . gg How Formed . 6g Cloud-banner . g g Moisture in Clouds gg Re-evaporation . -j Dew-point . ^1 Forms of Clouds 72 Altitude and Velocity . 7& Colour of Clouds Dust Particles in Clouds CHAPTER IV RAIN 78 Cause of Ram . gl Time of Greatest Fall . g2 Absorption and Percolation, etc. Amount of Rain . g5 Distribution of Rain . gg Extremes of Rainfall in 1905 . Tropical Rainfall . ^ Rainless Districts gl Impurity of Rain g2 Hardness of Rain-water gg Dust Particles in Rain-water . Rain-prints ' 95 Influence of Trees on Rain . ^ Signs of Rain . . CHAPTER V WATER . 108 Water . 108 The Composition of Water 112 Molecules of Water CONTENTS xi PAOK Specific Gravity of Water . . . . .113 Evaporation .... 116 Steam .... 117 Latent Heat of Steam ...... 120 Latent Heat of Water .... . 121 Specific Heat of Water . . . . . .122 Maximum Density of Water . 124 Congelation of Water ... 124 Cause of Expansion ... 125 Compression of Water . 125 Temperature and Pressure . . . . .126 Matter in Suspension . 126 Hardness of Water . . .127 Hardness and its Influence on Health . . . .128 Precipitation of Lime by Boiling . . . .130 Clark's Method of Softening . ... 131 Analysis of Chalk Water . .132 Analysis of Soft Water .... .132 Sea- water, Analysis of . . . . .133 Water in Articles of Food . . 136 The Aquarium ..... . 136 CHAPTER VI FORMS OF WATER, Etc. Dew 141 Hoar-frost ... 146 Sleet ........ 146 Hail ..... 147 Fog or Mist ... 148 Lightning and Storms .... .151 Waterspouts .... 154 Rainbows .... 155 Halos, etc. ... 156 Aurora Borealis ..... 157 Stalactites and Stalagmites . . 159 Stalactite Cave .... 160 ..... 166 CHAPTER VII SNOW Snow 172 How Snow is Formed ... 172 xii CONTENTS PAGE Snow Crystals ... ... 173 Transparency of Snow . . . . . .174 Snow as a Conductor . . . . . .176 Impurity of Snow . . . . . .177 Snow-line . . . . . . .179 Snowfields ....... 181 Avalanches . . . . . . .183 Floods 185 CHAPTER VIII ICE Ice . . . . . .186 How Formed ....... 186 Ice-flowers . . . . . . .188 Expansion and Pressure ..... 190 Heat given out by Freezing . . . . .191 Freezing of Lakes . . . . . .192 Freezing point of Sea- water . . . . .193 Ground, Bottom, or Anchor Ice . . . .194 Ice-fields . . . . . .195 Polar Expeditions ' . . . . .196 Icebergs . . . J . . . . 201 Ice-floes . . . . . . . 205 Ice-pack . .. . . . . . . 205 Sea Ice . . . . . . . 207 Icicles ........ 208 Ice Formed in Caves ...... 209 Extremes of Temperature (Arctic) . . . .210 CHAPTER IX GLACIERS Glaciers ........ 213 How Formed ....... 214 Rate of Travel ... . . . .215 Extent of Glaciers ...... 218 Tributary Glaciers . ... 220 Plasticity and Regelation . . . . .221 Moraines ....... 224 Erratic Blocks ....... 224 Sand-cones and Glacier-tables ..... 225 Crevasses, how Formed ..... 227 CONTENTS xni PAGE Moulins ........ 233 Ice-barriers ....... 234 Lakes formed by Glaciers ..... 235 Advance and Retreat of Glaciers .... 236 Glacial Period, the . . . . .237 CHAPTER X SPRINGS Springs ........ 244 Surface Springs ....... 245 Deep-seated Springs ...... 246 Fault Springs . . . . . . . 250 Submarine Springs . . . . . .251 Capillary Attraction ...... 254 Line of Saturation ...... 255 Intermittent Springs ...... 255 Effect of a Drought on Springs ..... 256 Influence of Rain on Springs ..... 257 Infiltration and Pollution ..... 259 Geysers ........ 261 Water as a Solvent ...... 264 Thermal or Hot Springs ..... 265 Thermal and Mineral Waters , 268 CHAPTER XI RIVERS Rivers ........ 275 Length ........ 278 Velocity ........ 279 Solid Matter in Suspension ..... 281 Matter in Solution ...... 283 Recession of Waterfalls ...... 284 Deltas, etc., formed by . . . . . . 285 CHAPTER XII WATERFALLS How Formed ....... 290 Victoria Falls 290 XIV Niagara Falls Great Kaieteur Fall CONTENTS I'AGE 295 296 CHAPTER XIII LAKES Lakes Crater Lakes, etc. Surface Level of Salt Lakes, how Formed The Dead Sea . Great Salt Lake, Utah, etc. Dried-up Lakes . Area of Lakes Temperature of Lakes . Colour of Lakes . . 301 304 305 305 307 310 311 312 313 Ocean and Sea . Area Depth . Pressure and Depth Temperature Colour . Power of Waves Ocean Currents . The Gulf Stream The Polar Stream Harvests of the Sea Marine Caves CHAPTER XIV OCEAN AND SEA 314 317 317 320 322 326 328 333 335 337 339 340 CHAPTER XV MOUNTAINS AND VOLCANOES Mountains Erosion and Denudation Altitude of Mountains . 344 348 348 CONTENTS xv I'AQK Influence of, on Rain ...... 348 Volcanic Mountains ...... 349 Volcanic Eruptions ...... 352 Earthquakes ..... 357 Volcanic Islands . . 359 CHAPTER XVI CHALK Chalk .... 361 Thickness of . . , . 3g4 Flint and Gravel in . . . . p 354 Disintegration ..... 365 Chalk as a Natural Filter-bed ..... 366 Specific Gravity of, and Water contained in . . , 367 Natural Chambers .... 368 Percolation in ..... 371 Adits in . . . . . . 371 Description of Adits . . 372 CHAPTER XVII DENUDATION The Forces at Work .... 375 By Change of Temperature ... . 377 By Chemical Action . . . . 377 By the Atmosphere . . 377 By Rain ...... .378 By Rivers and Streams ... 381 The Weald of Kent . . 381 The Isle of Wight . 383 The English Channel . 333 Animal Remains . . . 334 By Landslips .... 335 By Glaciers . . 3g5 Formation of Plains, etc. . . 387 River Terraces . . . 337 By the Sea ... 388 By Tides .... 391 xvi CONTENTS PAGE CHAPTER XVIII WATER, HOW OBTAINED Shallow Wells ....... 396 Deep Wells ....... 398 Adits ........ 401 Horizontal Wells and Upward Borings . . . 404 Cause of Accidents in Wells ..... 404 Artesian Wells ..... .406 The Passy and other Borings ..... 409 Borings in the Medway Valley . . . .413 Rest-level and Area of Exhaustion . . . .416 Water from Lakes and Rivers . . . . .419 Water from the Elan Valley, from Lake Vyrnwy, etc. . 420 Aqueducts ....... 424 The Coolgardie Water Supply . . . . .426 Reservoir Dams ...... 429 Filtration ....... 431 Covered Reservoirs ...... 432 Artificial Distribution of Water . . . . 435 CHAPTER XIX USE, ABUSE, AND WASTE The Work of Water ...... 437 Irrigation ..... . 438 The Nile and the Assuan Dam . . . .441 The Temple of Philae ...... 444 Canals ........ 446 Power of Falling Water ..... 448 Hydraulic Cranes, etc. ...... 455 Sports and Pastimes ...... 458 Waste of Water ....... 460 Waste of Water by Frost ... .461 Lavish Use or Abuse .... . 464 Domestic Waste . . . . . . .464 CHAPTER XX LESSONS FROM NATURE 466 LIST OF ILLUSTRATIONS The Inn Kiver, near St Moritz early Morning . Frontispiece FACING PAGE A Trilobite ....... 2 The Nebula in Andromeda ..... 2 A Piece of Chalk, magnified . . . . .12 To illustrate the Immensity of the Sun . . .12 Snow (not Cloud) blown from a Mountain Summit, Engadine 32 Typical Natural Waterworks ..... 38 Twilight (from Young's Astronomy) . ... 40 Atmospheric Kefraction (Dr Mill) . . . .40 Diagram of Area covered by Sun's Kays . . .44 Diagram of Thickness of Atmosphere traversed by Sun's Rays 44 The Cloud -banner of the Matter horn . . . .68 Sea of Cloud over the Lake of St Moritz while freezing . 70 A Cloud Study, Engadine . ... 70 Above a Sea of Cloud, Arctic Norway . . . .72 Clouds breaking like a Giant Waterfall over the Furggen Ridge, Matterhorn ...... 72 H.M.S. Phcenix driven ashore off Kowloon . . .74 Wrecked by the Typhoon, Kowloon . . . .74 The Matterhorn, from the Zmutt side . ... 80 Prehistoric Rain-prints on a Slab of Sandstone . . 94 Portion of the same Slab . . . . .94 Hoar-frost on a Tree . . . . . .146 A Network of Pearls (fog precipitated on a spider's web) . 148 Mountain Mists ....... 148 On the Matterhorn the way blocked by Mist . . .152 Above the Fog and Mist, 12,000 feet above sea . .152 The Alps from Belalp after a Storm . . . .154 Caverns of Han, Salle d'Embarquement . . .164 Snow Crystals . . . . . . .172 Crystallized Snow . . . . . .174 A Study of Snow in detail, taken at St Moritz . .174 xviii LIST OF ILLUSTRATIONS FACING PAGE 12,000 Feet above the Sea . . . . .178 Off towards the Matterhorn . . . . .178 A Corniced Ridge on an Engadine Peak . . .178 Snowfields from Piz Palii, Engadine .... 180 Crossing a Snow Bridge over a Crevaase (Sella Pass) . .182 The Remains of an Avalanche . . . . .184 A Train stuck fast in an Avalanche on Rocher de Naye . 184 An Avalanche blocking a Stream . . . .186 A Tunnel 300 feet long cut through an Avalanche . .186 An Avalanche Gully in Arctic Norway . . .188 An Ice-cave in the Morteratsch Glacier . . .188 Ice-flowers in the Alps . . . . . .190 The same spot twenty-four hours later . . . .192 The Ice-flowers at Close Quarters . . . .194 Detail of Petals of the Ice-flowers . . . .196 The Ice-flowers meet with an Untimely End . . .196 A Summer River of Ice . . . . .210 A Distorted and Crevassed Glacier (the Morteratsch) . . 214 Reflections on Glacier Lake, Arctic Norway . . .218 Glacier, Arctic Norway . . . . . .218 Tributary Glaciers ...... 220 Near Top of Monte Rosa, Tributary Glaciers and Moraines joining . . . . . . 222 The Monte Rosa Group from Wellenkuppe Glacier passing through a Narrow Gorge ..... 222 Rothhorn from near Unter Gabelhorn, showing the Moraine . 224 The Gb'rner Glacier and Moraine .... 226 A Glacier Table, Morteratsch Glacier .... 226 A Big Crevasse on a Snow-covered Glacier . . . 228 Ice-fall, Pers Glacier . . . . . .230 An Erratic in the Form of a Glacier-table, with Sand-cone . 230 Mont Blanc ....... 232 The Overhanging Cornice of Snow a frequent source of accidents ....... 232 An Active Moulin or Glacier Mill .... 234 A Shatter of Boulders, Arctic Norway .... 236 Glacier Lake, with Polished and Striated Rocks, Arctic Norway ....... 236 One of the Mammoth Tusks found in the Dry Chalk Valleys . 240 Sketch showing Curve and Sections .... 240 A Typical Surface Spring, Hollingbourne, Kent, issuing from the face of the North Downs .... 244 Plan showing the Dry Chalk Valleys, North Downs . . 246 LIST OF ILLUSTRATIONS xix FACING PAGE Section of Wells of Dry Chalk Valleys . . .248 The Origin of Springs (after Prestwich) . . . 252 Section to illustrate Intermittent Spring . . . 252 Diagram showing how a Fault may cause a Submarine Spring to be formed ...... 252 Geological Section, showing the different kinds of Wells and Springs, etc. ...... 254 Diagram showing the Effect of a Succession of Dry Years (1895-1902) ...... 256 A Deep-seated Spring in the Dry Chalk Valleys of the North Downs ....... 260 The Pink and White Terraces and Springs of Rotomahana, New Zealand ...... 266 Ice-cave formed in the Snout of the Loen Glacier by the Glacier Stream ...... 276 A Nearer View, showing Stream issuing from the Ice-tunnel . 276 The Natural Bridge and Gorge, Constantine, cut out by Water 280 A Beautiful Norwegian Waterfall near Trondhjem . . 282 To illustrate the Recession of Niagara .... 284 Section showing the Rocks at the Falls of Niagara . . 284 Niagara in Winter ...... 290 The Horseshoe Fall, Niagara . . . . . 292 The Gorge, Niagara ...... 292 The Zambesi Gorge ...... 294 The Swallow Falls, Bettws-y-Coed, North Wales . . 296 Waterfall, Ragaz, on the Road to Pfaffers, Switzerland . 298 A Lake on the Gorner Glacier between the Ice and the Moraine 300 A Glacier Lake formed by a Moraine, Artie Norway . . 300 The Lake of Geneva ...... 304 A Typical Mountain Lake . . . . .312 Typical Rough Sea and Coast Scene . . . .328 Coast Erosion at Southwold, Suffolk . . . 330 The same spot two days later ..... 330 Vegetation in Norway, 200 miles within the Arctic Circle . 336 Ice-lake in Arctic Norway, 2000 feet above the sea . . 336 The Azure Cave, Capri, Italy ..... 340 Hardanger Fjord, Norway ..... 342 Sor Fjord, Norway ...... 342 The Matterhorn from the Zinal Ridge of the Rothhorn . 344 Monte Rosa ....... 346 A Hanging Glacier on Ober Gabelhorn . . . 348 A Mountain Summit, Piz Bernina .... 348 Strood Waterworks Natural Chamber and Adit in the Chalk 368 XX FACING PARE The Natural Chamber, Strood . . . . .370 The Natural Adit, Strood . . . . .370 An Artificial Adit in the Chalk Formation, with Branches running in all directions to intercept the Water-bearing Fissures ....... 372 At the Bottom of the Well (the Bucket ascending with the Excavated Chalk) ...... 374 A Gendarme near the Ortler ..... 378 Section of the Weald of Kent ..... 380 Old Well-head, Snodhurst Farm, Kent . . .380 A Mountain Stream . . . . . . 382 The Bietschhorn ...... 386 The Birthplace of Glaciers view from Monte Rosa . . 388 Sections of a Deep Well ..... 398 Men and Tools employed on the Artesian Boring, Luton, Chatham ....... 400 The Author and Men boring with a 60-inch Chisel . . 400 An Artificial Adit in the Chalk . . . .402 An Artificial Adit in the Chalk Formation . . . 404 The Author's Method of controlling Underground Water during Extension of Adits . . . . 406 Diagram showing Adit driven into the Escarpment of the North Downs, Folkestone . . . . 408 Geological Section through the Paris Basin . . . 408 A Typical Artesian Boring . . . . .410 Exploding a Cartridge in a Deep Boring to increase the Yield of Water . . . . . . . 412 Geological Section illustrating how Water is obtained from both the Upper and Lower Cretaceous Formations at Chatham . . '.".". . 414 Enlarged Section of the Artesian Boring, Luton, Chatham . 416 Geological Section through the London Basin . . .418 The Vyrnwy Dam excavating the Trench across the River Vyrnwy ....... 420 The Vyrnwy Dam nearing completion . . . 422 Roman Aqueduct at Segovia, Spain .... 424 An enlarged portion of the same .... 424 Ruins of a Roman Aqueduct at Merida, Spain . . 426 Puente del Diablo, Tarragona, Spain .... 426 A Roman Aqueduct, Pont du Gard .... 428 The Water Channel, Pont du Gard . . . .428 A Covered Service Reservoir, 5,000,000 galls, capacity, in Course of Construction . . 432 LIST OF ILLUSTRATIONS xxi FACING PAGE The Iron Columns and Girders that support the Roof, with the Centering to form the Arches .... 432 The Assuan Dam across the Valley of the Nile . . 442 The Great Colgate Power House in the Sierra Nevada Mountains ....... 452 In a Cool Corner of my Garden .... 454 The Author measuring the Rainfall .... 454 The Cascades and Fountains of the Royal Palace of Caserta . 456 The Bath of Venus ...... 456 Skating . . . . . . .458 Tobogganing, Davos Platz ..... 460 Diagram from Electrical Water-Level Recording Apparatus . 462 The Valley of Celerina from St Moritz . . .468 Ice-ferns on Window Pane ..... 470 Portion of above photographed natural size . . . 470 An Erratic Boulder, Zermatt ..... 472 An Erratic Boulder with Osprey's Nest on Top . . 472 The Frozen River Medway, 16th February 1895 . . 476 WATER ITS ORIGIN AND USE CHAPTEK I HEAT In the Beginning " Before the hills in order stood, Or earth received her frame." To trace the story of water and its work we must go back to the very beginning of the earth's history. The word " beginning " is not intended to carry the mind of the reader back to that period at which it pleased God to create and disperse into space the marvel- lous elements of the material world, the Biblical descrip- tion of which is so familiar to us, and no verse of the Scriptures is more pregnant with mystery than the first : "In the beginning God created the heavens and the earth." This is not true, says Dr Harley, because it is found in the Bible, but it is found in the Bible because it is true. According to Euskin, " there are, broadly, three great demonstrable periods of the earth's history. That in which it was crystallized, that in which it was sculptured, and that in which it is now being unsculptured or deformed. 2 WATER: ITS ORIGIN AND USE These three periods interlace with each other as the periods of human life do ; of their length we know as yet nothing, except that it has been greater than any man has imagined." It will therefore be well to commence our story from the period of its crystallization, the study of which will unlock the past history of our planet, and, as Hugh Miller says, " will acquaint us with God's doings upon it, as the Creator of all, for myriads of ages ere He had first breathed the spirit of life into human nostrils, or man had become a living soul." This part of the Creator's work preceded all the divine accounts of the Creation which we read in the book of Genesis; it is also beyond the comprehension of the greatest astronomers and geologists that have ever lived. Of this period Dr Buckland writes: "It is nowhere affirmed that God created the heaven and the earth in the first day, but in the beginning. This beginning may have been an epoch at an unmeasured distance, followed by periods of undefined duration, during which all the physical operations disclosed by geology were going on." The evolution of our solar system from the original elements, as generally understood from the nebular theory of the renowned Laplace, is, as far as man is concerned, all we know of the beginning. But this is only a hypothetical theory, "it cannot be demonstrated by observation or established by mathematical calculation, but, from the study of other systems, astronomers have generally regarded this theory with considerable approval." According to Sir Norman Lockyer, a nebula consists of vast swarms of meteorites moving in different directions, and dashing against each other with such force as to generate sufficient heat to dissolve themselves into luminous vapour. THE NEBULA IN ANDROMEDA. A TRILOBITE. To face p. 2. IN THE BEGINNING 3 This globe was, then, but a iiebula, or a mass of gaseous matter, a fluid haze of light. The whole of our solar system, in fact, was evolved out of this immense nebula, which must have been thousands of millions of miles in diameter, similar to many now adorning the heavens. This rotating nebula, cooling by radiation of its heat into space, contracted and condensed towards the centre, leaving behind successive rings, in this manner giving birth to the planets, of which our earth is one of the smaller, and at last solidifying into and forming the sun as we see it to-day. Other astronomers, however, believe that the parent nebula assumed a pear-shaped form, and that the smaller end became detached, forming a planet with independent existence, and, as was the case with our own planet in its early days, self-luminous. The mass of solid matter now forming the sun and all the planets is said to represent only about one five- thousandth part of the mass of the original nebula. A study of this story will tell us how worlds like ours were so marvellously formed, and are now in the process of formation. Beginning with a state of gaseous vapour, we pass next to one of a mass of liquid matter of intense heat, and thence to the solidification of this molten mass. Throughout the gaseous period the immense body of matter surrounding the globe must have been millions of miles in thickness, and during this period water was present only in the form of vapour ; but, after a lapse of time, with the solidification there came a cooling, the reduced temperature was insufficient to maintain in a state of vapour the vast amount of moisture in the atmosphere, and the oxygen and hydrogen combined, giving birth to the water which now forms the oceans, seas, lakes, and rivers. 4 WATER : ITS ORIGIN AND USE Whether water was existing in the atmosphere during the molten period, in the form of rarefied steam, or as its constituent gases, oxygen and hydrogen, in an uncombined state, is unknown. It is certain that no water could have rested on this molten surface, the temperature of which must have been at least 10,000 F., a degree of heat almost beyond our comprehension, but one which we dare not question, for Sir William Crooks tells us that in the manufacture of diamonds it is necessary to raise the temperature of the electric furnace to 7200 F. According to Professor Sollas, liquid water (or, as I have seen it called, " wet water ") could not have begun to accumulate until the surface of the earth had cooled to 716 F. When it had cooled sufficiently, the water condensed and remained upon the earth, covering the whole surface. Owing to the heat of the earth, the evaporation and condensation were enormous. Rain fell upon the earth : but it was not cool, refreshing rain, with which we are familiar. It was a deluge of boiling water, described by one eminent scientist as red-hot rain, with a ceaseless accompaniment of thunder, lightning, and steam. How long this fierce battle between fire and water continued, we cannot say. Probably hundreds of thousands of years elapsed before the contest ended in water being victorious. It is certain that at this period there was a total absence of organic life upon the earth. None of the forms of life with which we are acquainted, or the remains of which have from time to time been discovered, could have existed in or survived the intense heat of this period. Many millions of years must have passed before the Creator of the universe saw fit to provide even the most primary form of organic life, and innumerable forms of IN THE BEGINNING 5 both animal and vegetable life had existed and passed away into geological history before it was deemed a fitting habitation for man. The preparation of the globe for all forms of life was impossible without water ; thus in these remote ages water had commenced its useful and necessary work a work, we shall see, it has never ceased to perform. " Of all physical agents," says Dr Buckland, " that have at any time and in any manner affected the surface and interior of the earth, in the foremost rank we find fire and water those two universal and mighty antagonistic forces, which have most materially influenced the condition of the globe, and which man has also converted into most efficient instruments of his power." "During the earlier ages of our globe," says Louis Figuier, " waters covered a great part of its surface, and it is in them that we find the first appearance of life. When the waters had become sufficiently cool to allow the existence of organised beings, creation was developed and advanced with great energy, for it manifested itself by the appearance of numerous and very different species of animals and plants." The crust of the earth is variously stated to be 30 or 40 miles thick, under which is a layer of molten matter 60 to 100 miles thick, the whole centre of the earth being gas, but under such pressure and of such great density as to be three times heavier than granite and as incom- pressible as steel. Further research, however, into the question of the thickness of the earth's crust has caused a much higher figure than the above to be stated. It is assumed that a thickness of at least 2000 to 2500 miles would be neces- sary to enable the earth to maintain its shape, the tide- producing force exerted by the sun and moon on our globe 6 WATER: ITS ORIGIN AND USE being sufficient to cause a deviation from its present shape, were it only, say, 100 miles thick. With the consolidation and buckling of the earth's surface, mountains were thrust up from the deeps, and vast continents began to appear above the heated waste of the waters, and it is apparent that "Then began the gathering together of the waters called seas, and the dry land appeared." The struggle for the mastery between fire and water continued intermittently ; for the earth was still passing through great convulsive changes, accompanied by earth- quakes and eruptions of internal fires, the crust of the earth gradually thickening. During these eruptions meta- morphic rocks and mountains were in process of formation. In all this water played, as we have seen, an important part, and practically "laid the foundation of the earth, that it never should move at any time." " We have traced back," says Dr Buckland, " the history of the primary rocks, which composed the first solid materials of the globe, to a probable condition of universal fusion incompatible with the existence of any forms of organic life, and have seen reason to conclude that, as the crust of the globe became gradually reduced in temperature, the unstratified crystalline rocks and stratified rocks pro- duced by their destruction were disposed and modified, during long periods of time, by physical forces, the same in kind with those which actually subsist, but more intense in their degree of operation ; and that the result has been to adapt our planet to become the receptacle of divers races of vegetable and animal beings, and finally to render it a fit and convenient habitation for mankind." Probably neither the greatest geographical or geological scholar, nor even the greatest living astronomer, is suffi- ciently acquainted with the universe, or the structure of IN THE BEGINNING 7 our earth, to speculate, without fear of contradiction, as to its age, or the duration of any of its previous forms. Eeferring to this subject, Sir Oliver Lodge remarks that " he did not know why it had taken so long to produce man upon the earth. That was a mystery of which he could only speak with bated breath, but he supposed that in a sense it could not be done any quicker with the same completeness or thoroughness. In the early years of existence the world contained only the lower forms of lifo, but it gradually improved, until it became what it is, and man attained his present state. But lower and higher forms still exist on the planet." Hugh Miller considers that the vast series of long geologic ages and their successive creations, each placed in advance of that which had gone before, are more worthy of their Divine Author than had the whole work been huddled into a few literal " days," " and thus convert the incalculably ancient universe which we inhabit into a hastily run-up erection of yesterday." The story of the successive geological periods and the gradual evolution of life, of the fossil remains of marine vegetation, of fishes, insects, land vegetation and terrestrial animals, is too vast a subject for further investigation here, and we must leave them to the geologist and the chemist, and proceed to the simpler wonders of creation, in which the work of water can be more easily traced than in the period just considered. It is, however, more than probable that life first had its being in these more or less heated waters ; and it is in this respect that the waters of the globe have been con- sidered by many to be the cradle of the world. The first dawn of life is variously stated as having taken place some forty or fifty million years ago. How this first gerrn of life (or protoplasm), the structural unit and 8 WATER: ITS ORIGIN AND USE basis of all organic bodies, came into being, and began its vital and endless function of evolution, culminating in man, none can tell. We can only believe that this life must have had a divine origin, or, as we term it, creation ; for it can only be begotten of life, and reproduced only by living organ- isms ; by no conceivable process could living matter arise from dead matter; but we do know that rocks formed of the sediment of the ancient seas have yielded the fossil remains of some of the earliest forms of life, which were of marine origin, but by no means the first life. One of the creatures referred to is the trilobite, a widely distributed family of extinct palaeozoic Crustacea, comprising more than fifty genera, which are found in the Cambrian and Silurian strata. They are so named from their bodies being divided into three lobes. These little creatures, which nature has preserved to us in fossil form, are probably 12,000,000 years old, and represent a very low form of life. Their marvellous construction will well repay the reader for any time he may spend in learning more of them. Solar Heat We have seen that, in the beginning, the atmosphere was heated principally by the earth itself. Continuing the history of our globe, there came a time when this heat was, for purposes of evaporation, practically insufficient. It has been ascertained that the amount of internal heat now escaping from the earth each year would be only sufficient to melt a shell of ice one-fifth of an inch thick over the whole surface of the globe. The atmosphere, therefore, found itself compelled to rely solely on the sun for its warmth. It will be necessary, therefore, for the purposes of this 9 story, to consider as concisely as possible heat and its relation to water. The heat of the sun is inseparable from any description of water and its origin. The sun controls the solar system. It is really the cause of water in all its forms. In short, the whole of nature depends for its very existence upon the energy imparted by the sun. It has been rightly called " the grand prime mover in all that circulation of matter which goes on, and has gone on for untold ages." In following water, therefore, through its varied and interesting phases, we must understand more fully the source from which all this power and work originates. The ancient inhabitants of our earth had a most erroneous idea of these matters. "They believed," says Sir Oliver Lodge, " that the earth was the centre of the universe, the world to which everything else was an appendage, a world with a sort of sky over it, in which there were lights which regulated our seasons. What is the earth to us ? A round globe, flying through space 19 miles every second of time around the sun ; one of a family the solar system ; smaller than most of the others, larger than some. Spinning round the sun, that sun only one of a myriad of smaller suns." We cannot do better in connection with this than quote the words of Sir Robert Ball : " To thoroughly obtain some conception of the intensity of the heat of the sun, we must imagine a temperature of molten steel, of such heat that it will run like water. Multiply this by seven, and we have then something approaching the fearful intensity of the celestial furnace that we see in the heavens. " The earth is a mighty globe, yet what are the dimen- sions of our earth in comparison with those of the sun ? If we represent the earth as a grain of mustard seed, then, on the same scale, the sun should be represented by a 10 WATER: ITS ORIGIN AND USE cocoanut. Again, look at the moon, which revolves round the heavens at a distance from the earth of 244,000 miles ; yet the sun is so large that if there were a hollow globe equally great and the earth were placed in its centre, the entire orbit of the moon would lie completely within it. " The solar heat is scattered through space with bound- less prodigality. The earth receives but an infinitesimal fraction of what the sun emits. The heat and light daily lavished by the sun would suffice to warm and illuminate 2,000,000,000 globes, each as great as the earth." Thus the earth receives only ^.-(jfffroVTLSou part, and the earth and the whole of the planets receive only s2T, /Lo combustion of of air at 62 lib. of fuel. chemically consumed. Coal of average composition 14*700 heat units 140 Coke .... 13-548 142 Wood, desiccated . . 10-974 80 Peat . . 12-297 99 Temperature Before leaving this subject, it will be as well to bear in mind that a thermometer measures temperature, and not heat directly. TEMPERATURE 19 Temperature is that energy with which one body seeks to impart its heat to another, and is no real indication of heat in the body, e.g. equal weights of mercury and water may have the same temperature, and yet the water will contain really thirty times more heat than mercury. Temperature implies that the condition of heat in a body may be compared with some standard, and the means of such comparison is the thermometer. The construction and use of the thermometer is so well known, that a general description is unnecessary, but it may be of some interest to know that mercury was not always used in its construction. Air has been used for this purpose : it was the substance first used by Sanctorius of Padua in 1590. His instru- ment consisted of a simple glass tube, having attached to it at one end a bulb, the other dipping into some liquid contained in a vessel below ; as the bulb became heated the air expanded, and forced down the liquid in the tube. Mercury, however, is found to be the most suitable substance ; and as the same body at the same temperature always has the same volume, and always suffers the same change in volume with the same change of temperature, we can easily understand how the change of temperature causes the mercury in the bulb to expand or contract, and so stand higher or lower in the tube, the amount of variation in the height depending upon the proportion which the diameter of the tube bears to the capacity of the bulb. Though the boiling-point of water varies according to atmospheric pressure, ice practically always melts at a fixed temperature of 32 F., so the zero of the F. scale is fixed 32 below this point. The interval between the points of freezing and boiling (212) is divided into 180 equal parts or degrees (32 + 180 = 212). In the centigrade scale the 20 WATER: ITS ORIGIN AND USE interval (32- 212 F.) is divided into 100, and the zero placed at the freezing-point. Mercury freezes at 39 or 40 below zero F., or 71 or 72 F. of frost. Glass is admirably suited for the bulb and tube of a thermometer, for it is found by experiment that the dilata- bility or expansive power of mercury is greater than that of glass in the proportion of nearly 20 to 1. It is also necessary that the tube should be made of some transparent material, so that the position of the mercury can be seen. If glass be heated from 32 to 212 F., the increase in volume is only '00001434, but mercury would be represented by -00014000. Where the heat to be measured is beyond the range of the mercurial thermometer, an instrument called the pyrometer is used. Internal Heat of the Earth The internal heat of the earth commands consideration here, as it is the principal agent in the formation of thermal springs, geysers, etc., to which we shall refer later on. It is found in temperate regions that at a depth of about 80 to 100 feet in the earth there is an unvarying temperature. All the world over, from the Arctic region to the tropics, varying of course with latitude, etc., there is a constant temperature at a certain depth. For instance, if it were possible to sink a shaft into the bed of the ocean to this depth, the result would be the same, the solar rays having no power to raise the temperature here. It is stated by Lord Avebury that "the variation of temperature due to the seasons, etc., does not extend to a greater depth than 5 feet into the surface of the earth." 4-8 in all things, however, there are exceptions to this INTERNAL HEAT OF THE EARTH 21 rule, and although the depth to which the seasonal varia- tions penetrate depends also partly on the thermal con- ductivity of the soil, rocks, etc., without doubt the cold of winter and the heat of summer are transmitted down- ward in successive waves, disappearing at the constant limit above referred to. In extreme climates, as we might expect, this zone of invariable temperature, however, reaches extreme depths. At Yakutsk, Eastern Siberia (Lat. 62 N.), in sinking a well the soil was found to be permanently frozen to a depth of 700 feet. The researches of Sir William Thomson prove how these apparently phenomenal conditions are possible. He says : " Any considerable area of the earth's surface, covered for several thousand years by snow or ice, and retaining, after the disappearance of that frozen covering, an average surface temperature of 13 C., would, during 900 years, show a decreasing temperature for some depth down from the surface, and 3600 years after the clearing away of the ice would still show residual effect of the ancient cold." In Java at 2 to 3 feet, and in India at a depth of 12 feet from the surface, the thermometer is constant all the year round. From observations made in the catacombs at Paris, which are situated at about a depth of 100 feet from the surface, there was no change of temperature ; this depth is called the invariable stratum, and is taken as having a temperature of 52 F. From observations taken all over the world, below the limit of the influence of the seasonal changes we have described, the temperature has in no single instance been found to diminish downward ; it always rises. Of course volcanic regions are excepted. Beyond the constant limit the temperature is influenced 22 WATER: ITS ORIGIN AND USE solely by the internal heat of the earth ; the difference between the temperature at 100 feet and at the surface is caused by what is called radiation. Below this depth there is an increase of 1 F. for each 66 feet, or 80 F. at the depth of a mile ; or at a depth of a little over 2 miles below the earth's surface the temperature would be 212 F. It is supposed that at a depth of 20 miles the temperature would be 1760 F., and at 50 miles 4000 F., at which point every known solid substance would melt. Some authorities give 1 F. for every 45 feet, others 52 feet, 55 feet, 60 feet, and 90 feet, but 66 feet appears to be generally accepted, the highest being 1 F. for each 41 feet at Glasgow, in the coal measures. These minor differences are no doubt due to local conditions : the kind of rock through which the heat has to pass, no doubt, has some little influence on the results. If this rate were kept up, the temperature at the centre would surpass the imagination of the most fertile brain ; but the increase cannot be as great as this would show, for if it were so, according to some estimates the tempera- ture would be not far short of 200,000 C. We only really know the condition of heat at a depth of from six to seven thousand feet. The hot springs which issue from the earth prove the existence of great heat within the earth, as also do active volcanoes. With our knowledge of these slumbering powers, there is little room to wonder when we hear of an eruption; it is indeed more wonderful that they should not be even more frequent and numerous, and of greater magnitude, than any we have records of. " The agency of central heat," says Dr Buckland, " and the admission of water to the metalloid bases of the earths and alkalies, offer two causes which, taken singly or con- INTERNAL HEAT OF THE EARTH 23 jointly, seem to explain the production and state of the mineral ingredients of the crystalline rocks, and to account for many of the grand mechanical movements that have affected the crust of the globe." From observations by the writer, the temperature of water in wells in the chalk formation 150 feet deep was found to be 53 F. ; in a well 250 feet deep, 56 F. ; and in an artesian well in the same locality, 650 feet deep (taken at the same time), 65 F., or an increase of 12 F. between 150 and 650 feet ; the difference between the two depths being 500 feet, giving an increase of 1 F. for each 41 '66 feet in depth. In making the Simplon tunnel (12 miles long), the tunnelling began from both sides simultaneously. The greatest obstacles encountered were springs of water yielding 3700 gallons per minute; finally, in the last section of the Swiss advance, a number of hot springs were met with, pouring out 600 gallons of water per minute at a temperature ranging from 104 to 117 F. The men at this point had 1 miles of rock over their heads. During the progress of this work careful observation was made, and it was found that the increase in tempera- ture was 1 F. to 71-5 feet, the figure being 977 F. at 2135 metres below the summit. At another position the vertical gradient worked out at 1 F. to 67'5 feet. This proves that though the increase of the internal heat of the earth is, as we have seen, 1 F. for each 66 feet all the world over, it will not account for the above temperature, which bears out the statement that where the heat is considerably in excess of these figures, it must be due to volcanic agency. It is, however, hardly satisfactory to take the tempera- ture of the water from springs, as in the above and similar instances, for comparison with the depth from which it is 24 WATER: ITS ORIGIN AND USE drawn ; for, though apparently coming from the level at which it is found, it is probable that it may really have its origin at either a higher or a lower level, and so carry an apparently inaccurate temperature. It must also be remembered that at some places both hot and cold springs issue from the earth within a few feet of each other. In the boring of the Ox-bow tunnel in Idaho, similar hot springs were met with, the temperature of which progressed from 95 to 132 F. at the hottest point; this difficulty was only overcome, and the work enabled to proceed by the usual method of spraying the walls with cold water. If we study the foregoing figures, a simple calculation will tell us what little distance we have to penetrate into the earth to come to temperatures such as that of our domestic fire (1100 F.), of the melting-point of wrought iron (2912 F.), of platinum (3080 F.), of a Bessemer furnace (4000 F.), and to that point at which the granite rocks would melt (20-30 miles). Such depths as these, compared with the diameter of the earth (7926 miles), are insignificant, and can be com- pared to the prick of a pin in the earth's crust. We who live on the surface of the earth would hardly give a thought to the existence of the enormous heat beneath us, were it not for the presence of volcanoes, geysers, etc., which remind us by occasional eruptions of their slumbering forces. CHAPTER II ATMOSPHERE " The great instrument of communication between the surface of the sea and that of the land is the atmosphere, by means of which a perpetual supply of fresh water is derived from an ocean of salt water, through the simple process of evaporation." Dr BUCKLAND. LET us now consider briefly the atmosphere of air which envelops the globe, without which nothing could live, nothing could burn, nothing could grow ; without which no sound could be heard, and there could be no rain. The more we think of this marvellous envelope, the more interesting and fascinating it becomes. Air is a mixture of two gases without chemical change, unlike water, which is two gases chemically compounded and forming a liquid. Dr Saleeby says: "For many centuries air was re- garded as a single thing, like water. "It had occurred to no one that air might be, as we now know it to be, a mixture of gases. This discovery was the work of Joseph Black, a Scotchman, the outcome of which was a revision of the doctrine of heat, the dis- covery of latent heat, and the universal acceptance of the fact that there is not only one kind of air." Impossible though it may appear to us, it is nevertheless a fact that, by a wonderful provision of nature, wet air is lighter than dry. One cubic foot of ordinary air at normal pressure (62 F.) 25 26 WATER: ITS ORIGIN AND USE weighs, when dry, 532'5 grains ; but if saturated, it weighs only 529 grains, or 3 grains less per cubic foot. Twenty thousand cubic feet of saturated air at 60 con- tain 17 Ibs. of water ; if the temperature of saturated air were 90, the same quantity would contain 47 Ibs. of water. The presence of this water vapour in the air has the effect of making a temperature of 30 to 40 feel raw and cold, 60 comfortable, 100 close and heavy as in a steam- ing hot-house. These same temperatures of dry air would not cause such extreme sensations. When the atmosphere is charged with vapour, and contains, in this form, all the water that is to become rain, etc., it is lighter than dry air; hence one of the minor causes of the difference in pressure shown by the mercury in a barometer, which then indicates rain, but actually shows reduced pressure. The probability of rain, of course, depends upon the presence of more or less vapour in the atmosphere, and in the progress of such changes as ultimately lead to its condensation. This is the secret of all the wondrous works accomplished by the atmosphere, beside which all other of nature's mysteries sink into insignificance. Were this not so, the whole existence of this globe would have been different ; and on this fact hang all the mysteries of the air, a few only of which we will try to trace. Maury says: "It feeds and nourishes the earth, it is more simple, more grand, more majestic than the world of waters, more varied and changeful in its moods of storm and calm, of ebb and flow, of brightness and gloom. "The carbonic acid with which to-day our breathing fills the air, to-morrow seeks its way round the world. The date-trees that grow around the falls of the Nile will drink it in by their leaves, the cedars of Lebanon will COMPOSITION OF THE ATMOSPHERE 27 take of it and add to their stature, and the palms and bananas of Japan will change it into flowers. " The oxygen that we are breathing was distilled for us some short time ago by the magnolias of the Susquehanna, and the giant rhododendrons of the Himalaya contributed to it. " It is an envelope or covering for dispersing light and heat over the surface of the earth ; it is a sewer into which, with every breath we draw, we cast vast impurities ; it is a laboratory for purification ; it is the machine for pumping up all rivers from the sea, and conveying the waters from their fountains in the ocean to their sources in the mountains." We will therefore devote a considerable portion of our story of water to trying to follow some of the methods by which the atmosphere fulfils these many duties, and acts as one of the principal of nature's agents, raising, purifying, and supplying to the world pure water and air, two of the things most necessary to our existence, and on which two things the whole universe lives and grows, and without which all other necessaries of life could never exist. The atmosphere is far older than the earth which it surrounds, consisting, as we have seen, of the remaining uncondensed gases left after the complete consolidation of the thin crust enveloping the earth, having, like the earth itself, gradually cooled down, until at last it has become capable of supporting life. Composition of the Atmosphere When we feel the breeze gently fanning our cheek, do we ever realise that the sensation is caused by molecules of air, so small that 25,000,000 of them, placed in a straight line, would only measure one inch, which are beating against our face although we cannot see them. 28 WATER : ITS ORIGIN AND USE The composition of air is as follows : By volume. By weight. Oxygen . . 20-84 23'141 Nitrogen . . . 79'16 76'859 100-000 100-000 It also contains '03 to '04 per cent., by volume, of carbonic acid. When dry it is 819 times lighter than water. The average proportion of aqueous vapour contained i-i air is 1*4 per cent, by volume. It is estimated that the total weight of the entire atmosphere of the world is 300,000 million tons. Sir John Herschel estimates it to weigh llf trillion pounds, and to equal in mass 7,500,0^ part of that of the earth itself. Fire could not be kindled without air, and to consume 1 Ib. of coal 11| Ibs. or 150 cubic feet of air are necessary to combine with it. Oxygen is a gas which is the most widely distributed of all the elements ; respiration, burning, and the produc- tion of light (electric light excepted) are only possible in its presence. (See Composition of Water.) It is the oxygen in the atmosphere that destroys metals, setting up rust or oxidation on iron; mercury (quick- silver) cannot withstand its influence under certain conditions. Iron rust weighs more than the amount of metal destroyed ; this additional weight is found to consist of oxygen, which by a chemical process can be re-converted into gas. It was by carrying out this experiment with red mercurial powder that Priestley, in 1774, discovered oxygen. The nitrogen which forms four-fifths of the atmosphere represents the inert negative element which, though not actively hostile to life, by diluting the oxygen, lessens the activity and rapidity of the energy developed by its ANALYSIS OF ATMOSPHERE 29 combustion, and thus tends to prolong life. Nitrogen is a colourless, inodorous, tasteless, incombustible, invisible gas, incapable of supporting life. Dr Schofield says that the human being, while resting, requires about 480 cubic inches of air per minute ; if walk- ing at the rate of 3 miles per hour, 1550 cubic inches; if running at the rate of 6 miles per hour, 3260 cubic inches. The average man requires, to replace the waste of his body, 7000 grains of oxygen and 300 grains of nitrogen daily. The other properties of these gases are of equal interest, but for the purpose of our story this must suffice. Analysis of Atmosphere The average composition of the atmosphere is : Oxygen 20'61 Nitrogen 7 7 '95 Carbonic acid .... '04 Aqueous vapour .... 1'40 Nitric acid ..... trace Ammonia ...... Carburetted hydrogen . . . T , I Sulphuretted hydrogen In towns \ ( Sulphurous acid . . 100-000 (According to Lord Eayleigh, air contains 1 per cent, of argon.) Specific Gravity of Elastic Fluids In order that we may be better able to trace some of the wonders of the atmosphere, it is necessary that we should know the specific gravity of air; and for our guidance and comparison the S.G. of a few elastic fluids are given. 30 WATER: ITS ORIGIN AND USE One cubic foot of dry atmospheric air, at 62 F., at normal pressure weighs 532-5 Troy grains ; its assumed gravity of 1 is the unit for elastic fluids. Therefore the specific gravity of Atmospheric air .... I'OOO Hydrogen -068 Oxygen M02 Nitrogen '971 Carbonic anhydride . . . 1*520 Steam at 212 F '488 Vapour of water .... -623 Carbonic Aeid in Atmosphere This is more properly known as carbonic anhydride, or carbon dioxide, and is composed of 12 parts by weight of carbon and 32 of oxygen ; it is a colourless gaseous com- pound, without smell, 22 times as heavy as hydrogen. It is incapable of supporting animal life ; in fact, if it exists in the atmosphere to an extent of only 4 or 5 per cent., it acts as a narcotic poison ; it however exists there in a harmless proportion of 1 volume to 2500. This compound plays such an important part in our story that we may with interest trace it a little further. It is disengaged from fermenting liquors, from decom- posing animal and vegetable matter. It exists in large quantities in all limestones and marbles, and is also found to emanate from the earth, constituting the choke- damp of the mines, the dangerous gas in our wells, vaults, and caves. From its weight it tends to subside into low-lying places, rendering them uninhabitable, as in the Upas Valley of Java. Thus we see that it is fatal to breathe carbonic acid ; it has its redeeming features, however, when taken into the EVAPORATION 31 stomach with our food. It exists in all aerated waters and beverages, from ginger beer to champagne, all of which owe their refreshing qualities to this gas. The amount of carbonic acid in the atmosphere has been found to be, in the London parks, '0301 ; London streets in summer, '0380 ; Manchester fog, '0679 ; worst parts of a London theatre, '3200 ; while in a mine in Corn- wall 2'5000 was found to exist. The extremely luxuriant forests that covered the face of the earth millions of years ago, before man's appearance, and which, by their rapid growth and decay, were destined to provide our present coal-fields, flourished and grew with great rapidity, covering the ground with their carbonaceous trunks, leaves, and branches. This prolific production of vegetable life was mainly due to the higher temperature then existing, and the greater proportion of carbon dioxide in the air ; it must have greatly exceeded what we find at the present day. In the accumulation and gradual decay of the luxuriant vegetable growth in the forests of past ages, which in course of time were buried and overwhelmed by floods, undergoing chemical changes, and suffering the loss of certain gases, we find a most interesting cycle of transformation, which, aided by gradual compression, resulted in the formation of coal. Evaporation The first process in the formation of cloud and atmos- pheric water is evaporation, or the conversion by heat of a liquid or a solid into vapour, which becomes dissipated in the atmosphere in the form of an elastic fluid. We will consider only the passing of water by natural process into the atmosphere, where it remains, generally invisible. 32 WATER: ITS ORIGIN AND USE If water be spilled upon the ground on a hot day, it dries up ; that is to say, it is quickly converted into invisible vapour. The small pool by the roadside, lakes, the mighty ocean, the fields of snow and ice, are all evaporating, eventually forming clouds and rain. Newly-fallen snow is at times the sport of the wind, and is frequently wafted from the summit of a mountain in the form of a vast banner. Professor Tyndall tells us he has seen it gradually melt away in the air, and again, by condensation, curdle up into true white cloud ; this in turn would be pulled asunder like carded wool, and reduced a second time to transparent vapour. The effect of evaporation is always to reduce the tem- perature of the evaporating surface. The lowest artificial temperature ever produced was obtained by the evapora- tion of volatile liquids such as ether. The evaporation from our bodies is one of the most obvious causes of diminution of temperature. We possess 2,000,000 perspiration glands, in connection with 10 miles of ducts. It is calculated that the available energy derived from oxidation of the organic matters of the food of a well- fed man equals about 2,700,000 units of heat (the unit being the amount of heat required to heat 1 gram of water 1 C.). Bodily heat is diminished by the skin, lungs, etc. By radiation and evaporation from the skin, about 75 per cent, is lost. In cold weather the loss by radiation is increased, and that by evaporation is proportionately decreased ; and under reverse climatic conditions we find a greater increase in the evaporation and a decrease in the radiation. The loss of bodily heat by the lungs is equal to 20 per cent., and is fairly constant at all temperatures. This accounts for 95 per cent. ; the remainder, 5 per cent., is disposed of in other ways. When a man is not exerting himself in any way, nature EVAPORATION 33 dissipates the heat from the body in the following manner : Units of Per heat. cent. In raising the temperature of food . 70,157 or 2 -6 In warming inspired air . . 70,032 2'6 In vaporising the water of the lungs . 397,536 14'7 Lost by radiation, conduction, and I ,.,,,,. f evaporation from the skin . ; 2,700,000 100-0 Here we see nature's system of evaporation and radiation at work in our bodies. If we apply this principle to the heat absorbed in the evaporation of water to form the vapour in the atmosphere, and set free in the re-condensation of the vapour into rain, it may perhaps help us to grasp this part of nature's wonders in connection with our subject. One other practical example of the reduction of temperature by evaporation. In hot climates water is made to freeze during clear, cold nights by leaving it overnight in porous vessels or bottles wrapped in moistened cloth. This is entirely due to the cold pro- duced by the evaporation from the porous vessel or by the evaporation of the water in the moistened cloth surrounding the bottle. Water requires a greater expenditure of heat to evapor- ate it than any other liquid. As much heat is required to evaporate a pound of water as would raise 966*6 Ibs. 1F., or about 5J Ibs. from freezing to boiling. (See Latent Heat of Steam.) This heat is stored up in the vapour, and given out again when the vapour is converted into water. In cold, cloudy weather we often hear the expression used, "It will be warmer after the rain " ; and there is more in this remark than a casual observation would lead us to think, for, 34 WATER: ITS ORIGIN AND USE "every gallon of rain that falls has yielded to the atmosphere that surrounds the place where it was con- densed as much heat as would raise 5^ gallons from freezing to boiling." Evaporation varies with the distance from the equator, and from many other causes. The glaciers, ice, and snow on the mountain summits, where the temperature is far below freezing, are continually evaporating. The sun pours its heat on the water in the tropics and evaporates it. Stored with this heat the vapour is borne away and converted into rain, giving up its store of heat when it encounters a lower temperature. Hartwig says: "Neither storms nor ocean currents, nor ebb and flood, however great their influence, cause such considerable movements of the waters, or force them to wander so restlessly from place to place as the silent and imperceptible action of the warming sunbeam." He considers that the whole of the aerial and terrestrial migrations of the waters of the globe are due to evapora- tion, and the counter-currents thus induced in both air and water. " To liquefy ice, a large quantity of heat is necessary. " To vaporise water a still larger quantity is necessary, as this heat does not render water warmer than ice, nor steam warmer than the water. "To convert a pound weight of tropical ocean into vapour, the sun would require to expend 1000 times the amount of heat necessary to raise 1 Ib. of water 1 degree in temperature." This same quantity of heat which would raise 1 Ib. of water 1 degree, would raise the temperature of 1 Ib. of iron 10 degrees ; thus to convert 1 Ib. of the tropical ocean into vapour, the sun must expend 10,000 times as much heat as would raise 1 Ib. of iron 1 degree in temperature. VAPOUR 35 " This quantity of heat would raise the temperature of 5 Ibs. of iron 2000, which is the fusing point of cast iron, when passing into the molten condition. "Imagine the mighty glaciers, etc., to be, instead of ice, a mass of molten iron, white hot and of quintuple the weight, and you get some notion of the enormous heat paid out by the sun to produce the present glacier. " This is as clear as day, and a diminution of the sun's rays would not produce an extension of our glaciers, but the reverse. " More heat instead of less, and the corresponding con- densation alone could produce a 'Glacial Epoch'" (Tyndall). Vapour Vapour is really the term applied to designate the gaseous form which a solid or liquid substance assumes when heated. Vapour is therefore essentially a gas, and most gases are now proved to be liquefiable. There is no physical difference between steam and vapour ; but for the purpose of our story we shall associate vapour with the natural passing of water into the atmosphere invisibly. Aqueous vapour formed on the surface of the land and water is always present, mixed with the atmosphere, and when it meets with a sufficient reduction in temperature, it condenses into water in the form of rain or dew, etc. If the air were perfectly dry, the heat radiating from the surface of the earth, as well as the solar radiation, would pass through it without it being sensibly warmed thereby add vapour and its diathermancy is diminished. So with an increase of vapour or with increase of humidity both solar and terrestrial radiation are much less felt on the surface of the earth. 36 WATER : ITS ORIGIN AND USE " Vapour is perfectly transparent to light, or luminous heat rays. It does not occupy more perhaps than ^^ of the space occupied by air : that is, it is present in very small proportion; yet it stops more than 100 times as much heat as all the air together 20,000 times as much as an equal quantity of air. "So impervious is it to heat, that no inconsiderable portion of the heat radiated from the earth is stopped within the first thirty or forty feet, probably not less than half. " Vapour water acts as glass ; lets the heat of the sun through, but will screen you from the heat of the fire. It also admits and then detains the heat of the sun. "The temperature of our planet is higher and much more equable than it would be but for this singular pro- perty of vapour " (J. M. Wilson). If vapour existed alone, and not in combination with air, as is fortunately the case, cloud would form only at one level. There would be only one temperature at which vapour could change into a liquid, and form rain. The level and temperature would alter with the time of day and season. Weight of Vapour "In pure dry air at sea level, with the barometer at 30 inches, we shall find that at 32 F. the column of mercury 30 inches high, resting on 1 square inch, weighs 14'7 Ibs., mercury being 13*6 times as dense as water, air only Y^g