UC-NRLF SB 27D 7fiD LIBRARY UNIVERSITY OF CALIFORNIA. RESEARCHES ON THE EARTH'S ATMOSPHERE. WORKS BY THE SAME AUTHOR FAMILIAR LETTERS ON SOME MYSTERIES OF NATURE. (London, 1876.) PHOSPHORESCENCE, OR THE EMISSION OF LIGHT BY MINERALS, PLANTS, AND ANIMALS. (London, 1862.) NOCTILUCINE, THE PHOSPHORESCENT PRINCIPLE OF LUMINOUS ANIMALS. (Pamphlet from the Chemical News, 1875.) THE UTILISATION OF MINUTE LIFE : PRACTICAL STUDIES ON INSECTS, CRUSTACEA, MOLLUSCA, ETC. (London, 1864.) METEORS, AEROLITES, AND FALLING STARS. (London, 1867.) LA FORCE CATALYTIQUE, . ETUDES SUR LES PHENOMENES DE CONTACT. (Gold Medal, Societe Hollandaise, Haarlem, 1858.) PHENOMENES METEOROLOGIQUES OBSERVES SUR LE LITTORAL DE LA FLANDRE OCCIDENTALS. (From the Comptes Rendus of the Paris Academy, 1857.) PHENOMENES LUMINEUX QUI ACCOMPAGNENT LES ESSAIMS D'ETOILES FILANTES. (Id., 1868.) SUR LES PROPRIETES OPTIQUES DES CORPS APPLIQUEES A L'ANALYSE. (Gold Medal, Societe Royale des Sciences Medicales et Naturelles, Bruxelles, 1868.) OUTLINES OF A NEW ATOMIC THEORY. (4th Ed. London, 1886. Pamphlet.) TRAITE DE CHIMIE A L'USAGE DES PHOTOGRAPHES. (i Vol. Paris, 1864.) EXPLOSION ET CHUTE DES METEORES. (Comptes Rendus, Paris, 1869.) ORIGINE DE L'OXYGENE ATMOSPHERIQUE. (Id., 1893 and 1895.) AGRICULTURAL CHEMISTRY OF THE SUGAR CANE, (srd Ed. Manchester, 1884.) MEMOIRE SUR LA FECULE. (Bruxelles, 1855. Pamphlet.) HEALTH NOTES AND CURIOSITIES OF MEDICAL SCIENCE, (i Vol. London, 1898.) VOICE AND VIOLIN, (i Vol. London, 1898.) FAMOUS VIOLINISTS, (i Vol. London, 1896.) SCENES FROM THE REIGN OF Louis XVI. (London, 1878.) (For other Writings, see " The Scientific and Literary Works of Dr. T. L. Phipson, with a short Biographical Notice," by C. J. BOUVERIE (London, Wertheimer, 1884), and Catalogue of Scientific Papers of the Royal Society of London, Vol. IV. and Vol. VII.) RESEARCHES ON THE PAST AND PRESENT HISTORY OF THE EARTH'S ATMOSPHERE Including the Latest "Discoveries and their "Practical ^Applications BY DR. THOMAS LAMB % PHIPSON AUTHOR OF "METEORS, AEROLITES, AND FALLING STARS"; "PHOSPHORESCENCE, OR THE EMISSION OF LIGHT BY MINERALS, PLANTS, AND ANIMALS " J " THE UTILIZA- TION OF MINUTE LIFE"; "FAMILIAR LETTERS ON SOME MYSTERIES OF NATURE"; "HEALTH NOTES AND CURIOSITIES OF MEDICAL SCIENCE"; "VOICE AND VIOLIN," ETC. LONDON: CHARLES GRIFFIN & CO, LIMITED EXETER STREET, STRAND. 1901 FRANK RUTTER, ESQ., B.A. (CANTAB.) THIS LITTLE WORK IS AFFECTIONATELY INSCRIBED BY THE AUTHOR TABLE OF CONTENTS. PREFACE, . . . Pages xi-xii INTRODUCTION. The Science of the Atmosphere Its Numerous and Important Applica- tions Origin of Modern Chemistry The Theory of Combustion History of the Chemical Composition of the Air Discovery of the Barometer, Pages 1-8 PART I. THE EARTH'S ATMOSPHERE IN REMOTE GEOLOGICAL PERIODS. CHAPTER I. The Atmosphere in the earliest Epochs of the Globe It contained no Free Oxygen The views of Koene, Berzelius, Mulder, Liebig, Dumas, and Ch. Martins The Author's Observations and Experiments Plants the first producers of Atmospheric Oxygen Fixation of Carbon in the Earth's Strata Diminution of Carbonic Acid in the Air The changeable Composition of the Atmosphere Gradual increase of Oxygen, Pages 9-14 CHAPTER II. Respiration in the Lowest Forms of Life Eremacausis on the Earth, . Pages 15-17 CHAPTER III. Plants are essentially Anaerobic Experiments by the Author Primitive Atmosphere of the Earth Vegetation in this Primitive Atmosphere and in other Gases, .... Pages 18-21 133489 vi TABLE OF CONTENTS. CHAPTER IV The Discoveries made by Priestley Mutual Dependency of Animals and Plants The Author's Experiments with Unicellular Algae The Author's Experiments with Convolvulus arvensis and other Plants, Pages 22-24 CHAPTER Y. Attempts to Define the Primitive Conditions of the Globe from the Results of Modern Research The Dawn of Animal Life Effects of the Gradual Increase of Atmospheric Oxygen, * Pages 25-31 PAKT II. THE ATMOSPHERE OF OUR PRESENT PERIOD. CHAPTER VI. The Atmosphere is only a Mixture of Gases, not a Compound Irrefragable Proof of this by Berzelius Its Changeable Composition The Inert Nature of Nitrogen Ammonia and Nitric Acid The Author's Experiments on their Mutual Conversion The Unexplained Phenomenon of " Nitrifica- tion" Its Universality Ammonia, like Carbonic Acid, a Volcanic Product Nitrification due to the Oxidation of Atmospheric Ammonia, Pages 32-37 CHAPTER VII. Definition of the Atmosphere of the Present Day Transparency Spectral Lines of Oxygen not given by the Sun's Atmos- phere Observations and Experiments of Janssen, Piazzi- Smyth, Langley, Dewar, and Faraday, . . . Pages 38-40 CHAPTER VIII. Sulphur always present in the Atmosphere Characin, the Cause of the Odour of Marshy Air Odours of the Air in Different Countries The Odour of the Sea- Air Detected by the Author in Marine Fossils of the Tertiary Period Odour of the Air after a Summer Shower Observations regarding Ozone, . . . Pages 41-47 TABLE OF CONTENTS. CHAPTER IX. The Electric Phenomena of the Atmosphere The Author's Researches and History of Electric Discoveries Phosphorescence of the Air Vibratory Nature of the Lightning- flash, . . Pages 48-54 CHAPTER X. An Unexplained Condition of the Atmosphere- Effects of Glare Snow-blindness Hemeralopia and Amaurosis, . Pages 55-58 CHAPTER XI. Solid Substances in the Atmosphere which fall to the Earth, or can be detected in suspension in the Air The Author's first Discovery of Iron Particles after the Meteor Stream of November 1866 Confirmed by other Observers His detection of Fossil Bacteria in the Air, and of minute Crystals of Ice His Observation of Bundles of Grass transported for hundreds of miles A Similar Observation by Boussingault in Venezuela Presence of Salt and Sulphate of Soda in the Air Gossamer Birds and Insects Cosmic Dust Explosion of Meteors Periodic Plants Trans- portation of Frogs, Stones, Volcanic Ash, etc. List of Extraneous Substances Mode of collecting Bacteria Observations by Pasteur, Miguel, and the Author, .... Pages 59-72 CHAPTER XII. Air essential to Sound Mountain Air Dr. Viault's important Observa- tion on Hsematosis Height of the Atmosphere Determination of Altitude Effects on the Barometer and Thermometer Tempera- ture at the Limits of the Atmosphere Hermite's recent Experi- ments with small Captive Balloons Heights of Clouds Determination of Water-vapour in the Air The Rain-band of the Spectroscope, Pages 73-80 CHAPTER XIII. . Air the only Gas that can be breathed Important "Work of the late Wilson Phipson The Compressed-air Work of Daniel Colladon Dr. Junod's Application of rarefied Air Air-bath Establishments Disinfection Special Action of given Disin- fectantsAbsence of Microbes in Pure Air, . . Pages 81-88 TABLE OF CONTENTS. CHAPTER XI V. Air of Inhabited Districts, of the Country, of the Sea-coast, and of the Ocean Quantity of Carbon in the Air of a London Music Hall Quantity of Carbon in the Atmosphere of the Earth Quantity of Carbon in Organized Beings The New Gas "Argon" Forest Air The Author's Observations in Waldeck, etc. The Influence of Trees on the Air of Towns Influence of Forests on Rainfall known to Columbus The Author's Explanation based on direct Observation, . . . . . Pages 89-95 CHAPTER XV. Cold Air more dangerous than hot Air The late Dr. Meisser's Opinion Effects of Sojourn in the Tropics Temperature Observations Altitude, Dryness, Humidity Carbonic Acid in London Fogs Air over Stagnant Water Hydrocarbon Gases in the Air of certain Localities The Air of Mines Air of Bedrooms Air of Fermentation Air of Wells and Sewers Air over active Volcanoes Air of the Mountains Effects of Arsenic Air of Treeless Plains Air of the Arctic Regions, and that near the Snow-line on Mountain-slopes Air of the Tropics Air in Cholera Epidemics, Pages 96-105 CHAPTER XVI. The Movements of the Atmosphere Barometer and Thermometer- Cause of their Reverse Movements Expansion of Air Diurnal Oscillations of the Atmosphere Fluctuations of the Electric State of the Air Velocities of the Wind Cause of the Move- ments of the Barometer English Weather Cyclones History of Rotatory Storms Small Local Cyclones, . . Pages 106-115 CHAPTER XVII. Absolute Weight of the Earth's Atmosphere Various Optical Phenomena caused by the Air The greatest height Man has reached on Foot The Snow-line and Region of Perpetual Ice, . . Pages 116-120 TABLE OF CONTENTS. CHAPTER XVIII. The Formation of Clouds The Vesicular Theory The Present Theory Cirrus Cloud Cumulus Cloud Stratus Cloud Nimbus Cloud Colour of Cloud and Sky as an Indication of coming Weather Cause of Electric Phenomena in Thunderstorms- Formation of Snow and Hoar Frost Formation of Hail Curious Phenomenon of the "Cloud-arch" First seen in England by the Author In Sicily by the poet Goethe In the Arctic Regions by Sabine, Pages 121-130 CHAPTER XIX. Influence of the Gulf Stream on the State of the Atmosphere over Europe and the Atlantic The Curve of Average Temperature and its Teachings, Pages 131-134 CHAPTER XX. Aerolites, or Stones from the Air "Thunderbolts" A Stroke of Lightning A Fall of Meteoric Stones Belt of Meteorites round the Earth Shooting-star Orbits, and Comets Old Opinion of the Indefinite Extension of the Earth's Atmosphere, Pages 135-139 CHAPTER XXI. The Organic Matter of the Atmosphere Effluvia, Miasma, Malaria, etc., Pages 140-144 CHAPTER XXII. State of the Atmosphere in any given Locality Immediate "Weather Table for the British Isles and Northern Europe generally Rainfall, %* . Pages 145-152 CHAPTER XXIII. Fogs and Electricity Ronayne's Discovery Luminous Fogs Prevention of Thunderstorms and Hail, . . Pages 153-157 TABLE OF CONTENTS. CHAPTER XXIV. Atmospheric Tides Magnetic Storms Sabine's Observations Absorption of the Moon's Atmosphere, , . Pages 158-162 APPENDIX A. Account of an Experiment made with Convolvulus arvensis Additional Notes, .... Pages 163-180 APPENDIX B., , . Pages 181-186 INDEX, Pages 187-194 PREFACE. THIS little work is to a great extent the result of my own observations, which have spread over a considerable number of years ; but I have also availed myself largely of the labours of others, in order to make it more com- plete, and more useful ; for, as Benjamin Franklin said, " Knowledge is only valuable in proportion as it can 'be rendered useful to mankind" I owe to my excellent father, to whom I dedicated one of my former works, everything that could foster the prosecution of travel and research, and, though I have not taken full advantage of the excessive liberality which he accorded to all his children, and cannot recall his memory without acknowledging the immense debt of gratitude with which it is associated, yet I trust that my numerous writings will prove " useful to mankind " for many years to come. However, his kindness and foresight have enabled me to devote my life to scientific pursuits, music, and literature, thus doing all he could to make it a life of happiness and contentment in spite of the sorrows and afflictions to which we are all subject in this world, and I have striven to make it also a useful life. The present volume contains the results of the latest xii PREFACE. discoveries connected with the vast aerial ocean which encircles the Earth ; the physical and chemical proper- ties of the air ; its geological history as far as we can trace it into the remotest ages of the past, and the useful deductions that can be drawn from all these facts. My discovery of the origin of atmospheric oxygen, made known in a series of papers published from 1893 to 1895 (Chemical News, London ; Comptes-rendus, Paris), and the curious results of that discovery, induced me to write this book, as so much interest is now taken in the subject, in all parts of the world. In the Philosophical Magazine for September and October 1900 are two papers by Mr. John Stevenson, M.A., communicated by Professor G. F. FitzGerald, F.E.S., on the chemical and geological history of the atmosphere, in which allusion is most indulgently made to "Dr. Phipson's beautiful and interesting experiments/' and in which Lord Kelvin's views are discussed. After a very long and interesting discussion, Mr. Stevenson confirms my opinion, declaring that " there was a time when there was no free oxygen upon the Earth," and also that " our present supply of free oxygen has been all produced by the action of sunlight on vegetation/' which is precisely what my experiments and observa- tions have established. CASA MIA, PUTNEY, LONDON. OF THE UNIVERSITY OF RESEARCHES ON THE EARTH'S ATMOSPHERE. INTRODUCTION. The Science of the Atmosphere Its Numerous and Important Applications Origin of Modern Chemistry The Theory of Combustion History of the Chemical Composition of the Air Discovery of the Barometer. THE Science of the Atmosphere embraces not only the whole domain of Meteorology the laws that determine the distribution of temperature, the cause of winds and cyclonic storms, the formation of fogs, clouds, dew, rain, snow, and hail, luminous manifestations due to electri- city, the phenomena of thunderstorms, ignis fatuus, and fire-springs, phosphorescent glows, mirage, halos, aurora, waterspouts, avalanches, and glacier movement, sand and dust storms, etc. but, also, the realms of Physical Geography, Geology, Chemistry, and Physiology the de- structive action of the air upon the Earth's surface, by its physical or mechanical action, and by its chemical action ; the phenomena of respiration in Plants and Animals, and its important consequences. 2 THE EARTH'S ATMOSPHERE. Hence the study of the Atmosphere includes certain branches of Medicine, antiseptic Surgery, and Hygiene, establishing the laws of Climatology, by which the practitioner is guided in the choice of residence for invalids. It also enables him to effect the promotion of health, and prevention of disease, by the detection of impure, noxious air, and by applying the art of rendering it wholesome. Moreover, it embraces, also, certain practical portions of Astronomy and Physics the laws of reflection, re- fraction, interference, absorption, pressure, electric con- dition, and magnetism. It is, indeed, a vast field of inquiry, and one that is practically inexhaustible; full of surprises inciting to research, and leading to endless useful applications. The Chemist and the Naturalist, the Astronomer and the Physician, are alike interested in acquiring the most perfect knowledge of the nature and phenomena of our atmosphere, which knowledge forms the basis of the greater portion of the sciences, and promotes the prosperity of the human race. The history of Chemistry the dawn of scientific chemistry is intimately connected with this subject, for modern Chemistry, with all its marvels of industry and invention, may be said to date from the discovery of oxygen. The advancement of the mechanical arts, promoted by the discovery of the barometer and its laws, is no less dependent upon an intimate acquaint- ance with the properties of that vast aerial envelope which encircles our globe, and is generally supposed INTRODUCTION. 3 to extend to a height of some forty-five miles from the Earth's surface. The knowledge of the chemical composition of the air is closely connected with the phenomenon of com- bustion the most wonderful of all the phenomena of Nature the theory of which forms the basis of modern science, and governs its useful applications to the wants of man. The ancients imagined a certain elementary body called fire, which possessed the property of devouring other bodies and converting them into itself. According to this view, which is still held by our domestic servants, when we set fire to a grate of coals we bring a small portion of the element fire which immediately begins to devour the coal and convert it also into fire. Whatever part of the coal is not fit to be this food is left behind in the form of ashes. It was in 1665 that the celebrated English philosopher Dr. Hooke (Micrographia, p. 103) first found that there exists in the Atmosphere a certain substance which is like that fixed in saltpetre. The French physician Jean Eey held a somewhat similar opinion thirty-five years previously. 1 In 1675 Hooke's opinion was adopted and extended by Mayow, a young man of Oxford, who published a pamphlet on the subject : De sal-nitro et Spiritus nitro-aereo, which is now celebrated in the annals of Science. 1 But about a century before this, the physician to Henri IV., Joseph Duchesne, called Quercitanus, a disciple of Paracelsus, who was also the inventor of laudanum, and the discoverer of the gluten of wheat flour, got the first glimpse of nitrogen. It was about the year 1573 he said that "saltpetre contains an air which extinguishes 4 THE EARTH'S A TMOSPHERE. Beccher, and his follower Stahl, came next with a singular theory (phlogiston) that threw men's minds, for a time, out of the correct line; and, strange to say, this phlogistic theory was kept up by Priestley, whose experiments on air, with those of Scheele and Lavoisier, finally led to the foundation of modern Chemistry. I cannot in this work devote space to the purely chemical investigations which gradually led us to a knowledge of the various gases which compose the Atmosphere. They must be sought for in treatises on the history of Chemistry and Physics. I can only say that, like all great discoveries, this knowledge was derived from the labours of a large number of ingenious men, among whom the most conspicuous are Van Helmont (of Brussels), Jean Eey, Bayen, Hooke, Mayow, Hales, Stahl, etc. To Priestley, Scheele, and Lavoisier is due the discovery of oxygen ; Black (of Glasgow) discovered the nature of carbonic acid. Nitrogen was actually discovered in 1772 by Dr. Eutherford, then Professor of Botany in Edinburgh (De Aere mephitico). Oxygen was discovered about the same time by Priestley, Scheele, and Lavoisier. In 1773 the latter gave us the first analysis of the air (finding 27 to 28 per cent, of oxygen, instead of 21). He began his researches in the flame of a candle" (Clavis philosophorum in Theatrum chemicum, iv. 1141, and Hoefer, Hist, de la Chimie, i. 471). In very ancient times Hippocrates recognized in air his "pabulum mice " (oxygen), and Democritus knew that it contained a vital principle which fixed itself in the body during the act of breathing. (See Aristotle, De Respiratione. ) INTRODUCTION. 5 1770, and finally announced in 1774 that "m every ease of combustion oxygen combines with the burning body" and from that moment the Science of Chemistry was revolutionized, or, rather, created. Yet years elapsed before he could make a single convert to his views! The labours of Cavendish on hydrogen (1774), and the speculations of James Watt and others, led to the knowledge of the composition of water. " Ozone," or allotropic oxygen, was discovered by Schcenbein of Basle in 1845, and " argon" (or " allotropic nitrogen " ?) by Eayleigh and Eamsay in 1894. The ancients, with Aristotle, considered air to be one of the " four elements " : fire, earth, air, and water. It was also believed to have no weight. In the early part of the seventeenth century an obscure apothecary named Brun, living in the little town of Bergerac, in France, noticed that when tin was melted over a hot fire, it formed a kind of earth (or, as we should now say, an oxide), and gained in weight. He asked a medical man of his acquaintance, Dr. Jean Key, who practised at the neighbouring village of Bugue, in Perigord, how he would explain this, and the doctor repeated the experiment several tiines. Finally, in 1630, he published a now celebrated pamphlet on the question, in which he declared that tin, when heated, absorbed air and increased in weight. This was a remarkable conclusion to arrive at, for in those days air was supposed to have no weight. More than a century later, when this pamphlet by Jean Key was quite forgotten, another French observer, 6 THE EARTH'S ATMOSPHERE. named Bayen, found that the same curious phenomenon occurred with mercury, and he concluded that all metals increased in weight when they were calcined. Finally, the celebrated Lavoisier repeated this experiment with mercury, and found that metals only absorb a portion of the air, that portion now known as oxygen gas. He thus made the first analysis of atmospheric air, as I have already stated. 1 The weight of the air was discovered in the following singular manner by the illustrious Galileo in 1640, and his opinion was soon confirmed by Torricelli (his pupil) and by the French philosopher Pascal. Galileo carefully weighed a large vessel full of ordinary air, and then the same vessel full of com- pressed air. A difference of weight was noticed, and this showed that the air was a body possessed of weight. Not long afterwards, some well-sinkers at Florence endeavoured to get water to rise more than 32 feet in a pump, and failing to do so, they asked Galileo the cause of this failure. In those days the rising of water in a pump was said to be due to the fact that " nature 1 Nevertheless, it has now been ascertained that this experiment is much older than has hitherto been supposed. It has been dis- covered that Eck von Sulzbach, a man usually confounded with the German alchemists of the latter part of the fifteenth century, was really the first to notice that metals increase in weight when calcined. His experiment was made with mercury, and with an amalgam of silver, and he distinctly states that this increase in the weight of the metal after calcination is due "to a spirit which fixes itself to the body of the metal," and he also says that when the latter " is distilled, this spirit is set free." Eck von Sulzbach made his second experiment in 1489, so that these facts had been ascertained nearly three hundred years before Lavoisier's experiment. (Compare Dr. F. Hoefer, Hint, de la Chimie.) INTRODUCTION. 7 abhors a vacuum"; and to explain the failure just alluded to, Galileo is reported to have replied: "Yes, nature abhors a vacuum, up to 32 feet, but not beyond." This little incident set his pupil, Torricelli, thinking over the problem. He imagined the rising of the water in the pump was due to pressure (or weight) of the air, and that this pressure was only equal to a column of 32 feet of water. He took a long tube of glass, filled it with another liquid, mercury, turned it upside down, and allowed its open end to rest on a bath of that metal. He saw that the column of mercury stood at a height of about 13 times less than that of the column of water in the tube of the pump, and as mercury is about 13 times heavier than water, it was evident that the same cause acted in both instances, and that cause was the weight (or pressure) of the air. Such being the case, the mercury in the glass tube should stand lower on the summit of a high mountain than in the valley, since it would have a less weight of air over it. This was proved to be so, by Pascal and Perrier, and so the barometer became at last one of the most useful of physical instruments in the hands of the meteorologist, the chemist, the physician, the sailor, the farmer, and the engineer. In bringing forward these modest contributions to so vast a field of research and observation, I must solicit a large amount of indulgence on the ]5art of my readers. It is not my desire simply to reproduce here what is to be found in standard works on Meteorology, but to give, as well as I can, the results of my own personal obser- 8 THE EARTH'S ATMOSPHERE. vations with as many new facts as possible, whilst I rely, for the rest, on the useful and interesting nature of the facts recorded. I trust that my little work will thus help to diffuse more exact knowledge with regard to the nature and properties of atmospheric air, and so contribute to promote, in many ways, the welfare of mankind. The atmosphere, as we know it at the present day, forms over the surface of the globe a vast layer of invisible gas, extending to a great height, and charged with emanations of all kinds, but chiefly of aqueous vapour. When we subtract from it this aqueous vapour, and a minute amount of carbonic acid, it is found, in all parts of the world, to consist of a mixture of two gases, nitrogen and oxygen, in the proportion of 79 of the former to 21 of the latter. 1 1 The new gas called "Argon " recently discovered in small quantity in the air by Lord Rayleigh and Prof. Ramsay, to which I make reference in another part of this little work, appeared to be a peculiar form of nitrogen, similar to what ozone is as regards oxygen. I was the first to call attention to this circumstance in a note inserted iu the Chemical News (1894), and my opinion has been since confirmed by Prof. Berthelot of Paris (Comptes-rendus, March 1895). Prof. Dewar seemed to be of the same opinion. It might also be a compound of carbon and nitrogen, containing half as much carbon as cyanogen ; such a compound would have the same specific gravity. But it is impossible at the present time to speculate upon the real nature of this new substance, as so very little is known about it. One hundred volumes of atmospheric air contain less than one volume of " argon," and its name is due to its inert nature, its negative properties being apparently greater than those of nitrogen itself. But whatever may be its real nature, argon is only present to such an insignificant amount (barely 1 per cent.} that it can exert no influence upon the general properties of the air, nor, considering its inert character, upon animal or vegetable life. PART I. THE EARTH'S ATMOSPHERE IN REMOTE GEOLOGICAL PERIODS. CHAPTEK I. The Atmosphere in the earliest Epochs of the Globe It contained no Free Oxygen The views of Koene, Berzelius, Mulder, Liebig, Dumas, and Oh. Martins The Author's Observations and Experiments Plants were the first producers of Atmos- pheric Oxygen Fixation of Carbon in the Earth's Strata Diminution of Carbonic Acid in the Air The changeable Composition of the Atmosphere Gradual increase of Oxygen. WATER and air the first a chemical compound, the second a mixture only have been considered by modern authors as the Residues left in primeval times after the cooling of the Earth, residues of stupendous chemical action, the formation of which rendered the surface of the globe fit for the existence of organized beings. But, was the air in those primitive periods such as we now know it ? Everything points to the fact that the chemical con- stitution of the atmosphere has varied in successive ages, just as the various flora and fauna of the Earth have changed. io THE EARTH'S ATMOSPHERE. The presence of certain combustible substances, such as iron pyrites, copper pyrites, molybdenite, graphite, etc., in the primitive rocks, long ago appeared to me to prove that no free oxygen could have l)een present in the atmosphere when these rocks were formed. The late Prof. C. J. Koene, of the University of Brussels, admitted that carbonic acid must have been present in the ancient atmosphere of the globe in much larger quantities than at present, especially during the period of the coal flora, which notion appears to be proved by the enormous residues of coal and anthracite, as compared with the more recent deposits of lignite and peat. Four great names appear also in connection with this subject : Jean Baptiste Dumas and Justus von Liebig on the one hand, Berzelius and Mulder on the other. The two former appear to have considered the chemical composition of the atmosphere of our globe to be per- manently fixed for an indefinite period, and, perhaps, they admitted it always to have been so since the first appearance of life upon the Earth, resting their views on the fact that whilst plants give out oxygen and absorb carbonic acid, animals absorb oxygen and reject carbonic acid. Dumas and Liebig looked upon the animal and vegetable kingdoms as indispensable one to the other, and believed that their mutual action upon the atmosphere would keep its composition constant. Charles Martins, a celebrated French naturalist, and a contemporary x)f Dumas, criticized this compensation EARLY GEOLOGICAL CHANGES. 11 theory, by pointing out the extremely minute quantity of air which is affected by the respiration of plants and animals, as compared with the vast bulk of oxygen in the atmosphere. Making use of Dumas' own calcula- tions, he shows that the atmosphere containing, say, 134,000 cubic measures of oxygen, the entire animal world only consumes about 15 of these in an entire century. Hence, he says, "The constant composition of the air does not depend upon a pretended equilibrium between the respiration of plants and animals , but upon the fact that the quantity of oxygen consumed by animals is out of all proportion to that contained in the entire atmosphere." 1 Berzelius felt convinced that oxygen must gradually diminish in the air, for, he declared he knew of " no de-oxydizing process sufficiently great and general to set at liberty all the oxygen which combines every instant with combustible material." 2 The great Dutch chemist, Mulder, went still further ; he insisted upon the enormous production of carbonic acid by the respiration of animals, fermentation, volcanic action, and human industry, and noted the constantly increasing destruction of forests, those vast manufac- tories of oxygen gas. He concluded that carbonic acid must increase, and that oxygen has continued to decrease since the first appearance of life upon the Earth. With regard to volcanic action, I myself have calculated roughly, on the spot, the quantity of car- 1 Mtttoroloyie et Physique du Globe. 2 Traite de CMmie t vol i. 12 THE EARTH'S ATMOSPHERE. bonic acid produced by a small chalybeate spring near Neubau in the principality of Waldeck (Germany) in the year 1865. It was somewhat over a pound in weight per hour, or about half a hundredweight in the twenty-four hours. And this is only one of some thousands of similar springs scattered over the surface of Europe alone. Dr. Koene upheld a precisely contrary opinion to those just mentioned: he admitted that the carbonic acid and nitrogen of the atmosphere have never ceased to diminish since the origin of living creatures, whilst the relative amount of oxygen has gone on increasing in proportion. I shall show that oxygen has really increased ; and, such being the case, nitrogen and carbonic acid will, of course, appear to have diminished. It seemed very evident to me that as there could have been no free oxygen in the primitive atmosphere of the Earth, the first living beings must have been formed in an air composed of nitrogen, containing some carbonic acid and vapour of water. They must have been anaerobic, that is, capable of existing without free oxygen', and it is interesting to note that some fifteen years after Koene professed his theory, Pasteur actually discovered anaerobic microbes and described their functions in fermentation, etc. It then struck me that plants were the first producers of atmospheric oxygen, and that they have produced it in constantly increasing quantities as ages rolled by, iintil the air acquired the composition it now has ; and, EARLY GEOLOGICAL CHANGES. 13 finally, I undertook a long series of experiments l with the view of testing this theory. By adopting the views of Lamarck and Geoffroy de St. Hilaire, followed up by Darwin and his friends, it would be easy to admit that these first producers of free oxygen these anaerobic beings, consisting, in the first instance, of the lower orders of plants such as the Protococcus, or unicellular algae, on which I experi- mented many years ago, and found that, weight for height, they produced far more oxygen than the higher plants would, in process of time, as the quantity of oxygen in the air became greater, gradually become more or less aerobic, and finally completely so. ... Ferdinand Hoefer's opinion that plants first appeared is stated in the following lines : " Starting from the theoretical view of the gradation of organized beings, and looking upon vegetable life as a necessary condition of animal life, the former must, consequently, have appeared before the latter." 2 Alexander von Humboldt made a rather weak attempt to disprove this by alluding to the fact that the Esquimaux live almost exclusively on fish and cetacea. An immense quantity of carbon is fixed in the Earth by the remains of plants and animals, and never returns to the air. Nitrogen ,is also supposed to be extracted from the atmosphere to form nitrates 1 Comptes-rendus de I'Acad. des Sc., Paris, Aout 1893 and 1895, and Chemical News, London, 1893 and 1894. 2 Histoire de la Botanique. 14 THE EARTH'S ATMOSPHERE. and ammonia ; but I shall show that this is not the case. Oxygen alone remains in relatively larger and larger proportions ; it has increased since the first living beings appeared, and its present maximum coincides with the maximum development of the central nervous and brain tissue of the animal world. As for carbonic acid, for the last half century chemists have noted it as only 6, 5, and 4 parts on 10,000 parts (volumes) of air. The latest determinations by Eeiset (a very careful chemist, pupil of Boussingault, and one of the editors of Millon's well-known Annuaire), made at a country place, many miles from Paris, gave only 3 volumes of carbonic acid on 10,000 volumes of air in 1889, and he could not get a fraction more. Pelouze, master of the Mint at Paris, who was one of the most expert chemists of modern times, held the opinion that the atmosphere might be undergoing very slight variations which will only become appreciable to analysis after a great number of years. Baudrimont, and other eminent chemists have held similar views, admitting that the so- called fixity of composition is only apparent, not real. CHAPTER II. Respiration in the Lowest Forms of Life Eremacausis on the Earth. ANATOMY and physiology cannot teach us how respira- tion is effected in the lowest creatures in the scale of life, those which are supposed to have been the first produced. All vestiges of a respiratory organ are absent, unless it be the cell wall or outer envelope that breathes. Until my recent experiments were made (which, however, were preceded in another direction by those of Pasteur, when he discovered the anaerobic ferments), no one could say whether these beings require free oxygen or not ; though this could be proved for higher organisms, such as fish and tadpoles, which live in water. I found that the microscopic unicellular algae, Protococcus pluvialis, P. palustris, etc., carry on their respiratory functions much as the higher organized plants do, but with more energy. In such animals as ffolothuria tululosa, the functions of respiration is little, if at all, separated from that of the intestine : water is sucked in, three times a minute, and remains about twenty seconds in the animal's body. 1 6 THE EARTH'S ATMOSPHERE. It is not yet known with certainty whether these lower forms of life may be able to derive oxygen from water, or carbonic acid, or both. But it is evident that oxygen is essential both for plants and animals, how- ever low in the scale ; in fact, that oxygen arid life seem to be synonymous terms in this respect ; only, we must distinguish between oxygen in combination, and the free oxygen of the atmosphere. Koene's ingenious theory to which I have alluded is based upon the incomplete eremacausis of organic matter which is confided to the earth, and protected from the action of the air, by which means enormous quantities of carbon have always been, and are still being, slowly subtracted from the atmosphere. He did not believe that this element can be supplied from without from cosmic space and it thus disappears for ever from our atmosphere. But is this eremacausis, or slow combustion, really so incomplete ? Is not carbonic acid returning in immense quantities to the atmosphere, not only by the respira- tion of animals and volcanic action, but by the agency of man himself ? In times, perhaps not so very far distant, will not the whole of those vast deposits of coal and lignite, formerly taken from the air, return to the atmos- phere again as carbonic acid ? And if forests continue to be constantly annihilated, as Mulder remarked, to make room for clay and stone buildings, will not car- bonic acid increase, until it once more predominates, as it is supposed to have done in primitive times? It seems evident to me that vitality, nervous power, RESPIRA TIONEREMA CA US IS. 1 7 and atmospheric oxygen have increased together, from the earliest ages of the globe, and that the history of this increase can be read in the records of the Earth's strata. Although, as will be seen presently, my researches bear out this theory of the increase of oxygen in the atmosphere, it presents, at first sight, a curious para- doxical aspect: oxygen is admitted to be the product of life, whilst it is the condition of life, and its final predominance in the atmosphere will, perhaps, be the cause of universal death. Certainly this appears highly paradoxical ; and it may be questioned whether the solution of such problems is not beyond the powers of Science, like all those which touch upon creation. But, as I have already remarked, we must distinguish between oxygen, and/m oxygen in the atmosphere. CHAPTEE III. Plants are essentially Anaerobic Experiments by the Author Primitive Atmosphere of the Earth Vegetation in this Primitive Atmosphere and in other Gases. ADMITTING that no free oxygen could have existed in the atmosphere when life first appeared upon our globe, and that this atmosphere must then have consisted of nitrogen, containing more or less carbonic acid, and vapour of water, it follows that atmospheric oxygen must originally have been derived from the vital functions of inferior plants such as the unicellular algae, which were the first created beings, having the power, under the mysterious influence of the solar rays, of separating it from its compounds, carbonic acid and water. Granting that the ancient cryptogamic plants of the Coal flora period, for instance, could thrive at higher temperatures, and in an atmosphere far richer in carbonic acid than that of our own day, it became very interesting to ascer- tain to what extent our modern plants can vegetate under similar circumstances. It was in making experiments to this effect I dis- covered that all plants are essentially anaerobic. I have caused them to vegetate in carbonic acid, in ANAEROBIOSIS. 19 hydrogen, and in nitrogen, as well as in a mixture of nitrogen, carbonic acid, and vapour of water repre- sentative of the "primitive atmosphere" at the time life first appeared. I was thus gradually led to conclude that the primitive atmosphere of the Earth was nitrogen, into which volcanic action poured more or less carbonic acid and vapour, and that after vegetable life appeared, free oxygen made its appearance in the air, and has increased in quantity from those primitive times to the present day. I had noticed many years ago that certain plants (willow, lilac, etc.) did not thrive in pure carbonic acid, and I concluded that the diminished quantity of this gas now existing in our atmosphere was the condition that suited them best. In experiments carried out more recently, I have placed various other plants, such as Poa, Agrostis, Myosotis, Antirrhinum, and Convolvulus in an atmos- phere composed of pure carbonic acid, and in one composed of air with about a hundred times more of this gas than exists in our atmosphere at the present day. All other conditions of vegetation were normal : there was ample water, mineral elements, and an appropriate temperature ranging from 59 to 70 Fahr., during the whole course of the observations. It was not long before I found that my plants could exist for many days, or even weeks, in an atmosphere of pure carbonic acid, but they did not thrive ; cell formation became slower and slower, in spite of a constant good light. 20 THE EARTH'S A TMOSPHERE. In an atmosphere that contained so much carbonic acid that an animal exposed to it would perish in a few minutes, all my plants lived for many weeks, and appeared healthy. In an atmosphere containing one hundred times as much carbonic acid as in the natural state of the air in our day, my plants flourished remarkably well for the whole time that the experiment lasted a month, or six weeks. It was thus rendered highly probable that in former geological periods there existed plants which could flourish in an atmosphere excessively rich in carbonic acid, and that the quantity of that gas in the air has really decreased from those times to the present day ; the loss being represented by the vast deposits of peat, lignite, coal, and anthracite found in the strata of the Earth. I also made some experiments in an atmosphere of pure hydrogen, out of curiosity to see what would happen when plants were placed in such a medium a gas which many have looked upon as the vapour of a metal all other conditions remaining normal, namely, water charged with carbonic acid, and containing the necessary mineral ingredients, and a steady source of daylight. The plants I placed in this atmosphere of pure hydrogen were Convolvulus arvensis (a plant which is very convenient for observation of this kind), and a small specimen of Antirrhinum majus. For the first few days nothing peculiar was noticed. From ANAEROBIOSIS. 21 the 27th May to the end of the month a slight bleach- ing of the leaves only was apparent, but by 3rd June a singular phenomenon occurred: the volume of gas began to diminish, and in the course of another month the atmosphere of hydrogen in which the Convolvulus vegetated was absorbed to the extent of about 80 per cent. The residue, 20 per cent., was found not to be hydrogen; so it may safely be said that the whole of the hydrogen had disappeared, the plant remaining perfectly healthy. I can only explain this phenomenon by assuming that the nascent oxygen emitted by the leaves burns up the hydrogen, and converts it into water. The same thing occurred with the Antirrhinum, but the action was slower. In both cases the leaves were slightly bleached, and as the water charged with carbonic acid rose in the apparatus and covered them, they became green again. In all these experiments the plants were exposed to the constant light of a northern sky, such as artists use for painting. The rapidity of cell formation in an atmosphere of hydrogen gas, observed in the case of Convolvulus arvensis, was highly remarkable. CHAPTEE IV. The Discoveries made by Priestley Mutual Dependency of Animals and Plants The Author's Experiments with Uni- cellular Algce The Author's Experiments with Convolvulus arvensis and other Plants. IN 1791, when Dr. Priestley's house was burnt by the Birmingham mob, and he saved his life by escap- ing in my grandfather's carriage, a considerable amount of valuable silver plate, etc., was carried off, but none of the still more valuable MSS., the results of years of labour. These were destroyed, together with the entire library and laboratory. It is therefore impossible to say how far he may have pushed his investigations with regard to the mutual dependency of plants and animals after discovering, some twenty years previously, that " a sprig of mint vegetating for a few days in an air vitiated by a burning candle restored the purity of that air sufficiently to allow the candle to burn in it again." In the seventh edition of the Introduction to Botany, by Sir J. E. Smith, edited by William Hooker (1803, page 104), the author, alluding to the absorption of carbonic acid by plants, and its replacement, volume OXYGEN AND ITS DEVELOPMENT. 23 for volume, by oxygen gas, says: "This beautiful discovery, for the main principles of which we are indebted to the celebrated Dr. Priestley, shows a mutual dependence of the animal and vegetable kingdoms on each other, which had never been suspected before his time." It is not probable, however, that Priestley could have made much further advance in this direction, owing to the backward state of chemistry in his day, and to his zeal for political and religious discussions. It was reserved for the persevering researches of the Swiss chemist, Theodore de Saussure, and to the splendid genius of Justus von Liebig, to demonstrate this mutual dependency in all its striking realities. Yet it is greater than even Liebig imagined ! After having found that minute microscopic plants, such as .the Protococcus pluvialis and P. palustris (uni- cellular algae), could be easily transformed, so to speak, into manufacturers of oxygen gas, 1 and that they produced it more rapidly than do the higher plants of our epoch, I placed several kinds of the latter in pure carbonic acid, and found that it did not kill them at once, as it would kill an animal, but that they lived in it for some time, though they did not prosper. In an atmosphere of hydrogen they lived and prospered ; but the hydrogen gas was slowly absorbed, as we have already seen, until it had all disappeared. In the next place I exposed my plants to an atmosphere of pure 1 Phipson, "Production of Oxygen by Protococcus pluvialis" (with figure of the apparatus), Chemical News, 1883 ; " The free Oxygen of the Atmosphere," ibid., November 1894. 24 THE EARTH'S ATMOSPHERE. nitrogen, and to what I may term a " primitive atmos- phere," consisting chiefly of nitrogen, with some carbonic acid and vapour of water, and I found that, in both cases, vegetation was remarkably healthy, and even luxuriant, for a lengthened period. A small plant of Convolvulus arvensis, having its roots in the soil, or in water containing ample carbonic acid and mineral ingredients, vegetated in an atmosphere of pure nitrogen for ten days (22nd June to 2nd July). I then let in carbonic acid, an equal volume, which in twenty-four hours was absorbed by the water to the extent of about one-half ; so that the artificial atmos- phere, on the next day, consisted of about three volumes of nitrogen and one volume of carbonic acid. In this atmosphere the vegetation became truly luxuriant from the 2nd to the 15th July, and would doubtless have con- jfcinued much longer had not the experiment been stopped in order to analyse the gas, and because the plant had reached the summit of the apparatus, and was pressing against the glass. In another similar experiment the residual gas, after fourteen weeks of vegetation, was found to be richer in oxygen than ordinary atmospheric air. 1 In these experiments the plant appears to absorb carbonic acid by the roots (as well as the leaves), whilst it evolves oxygen by the leaves ; so that, after awhile, the nitrogen atmosphere contains a certain quantity of oxygen and, in time, approaches, or even surpasses, the composition of ordinary air. 1 See APPENDIX for fuller account of this experiment. CHAPTER V. ' . ij ' Attempts to Define the Primitive Conditions of the Globe from the Results of Modern Research The Dawn of Animal Life Effects of the Gradual Increase of Atmospheric Oxygen. Now, if I endeavour in thought to go back to the primi- tive ages of the globe, I find that there was probably a period at which the heat was so intense that no com- pounds could exist. The matter of the Earth then existed in the state of free elements, or, according to my own theory, 1 in the state of atoms all identical. As the temperature decreased, compounds of all kinds were formed according to the laws of affinity; and, finally, there remained, surrounding the solidified sur- face of the Earth, an atmosphere of nitrogen a substance which is known to have no tendency to combine directly with other substances. That there was no free oxygen in this primitive atmos- phere is evident from t the presence of various oxidizable substances in the primitive rocks of our globe. It is into this primitive atmosphere of nitrogen that plants have poured oxygen, year after year, for countless myriads of 1 Phipson, Outlines of a New Atomic Theory, fourth edition, London, 1886. See APPENDIX. 26 THE EARTH'S ATMOSPHERE. ages, until it has attained the composition which it has at the present day. In remote geological periods it may have contained much more carbonic acid than at present ; but carbonic acid could never have predominated, from the fact that it would have been absorbed by the waters of the oceans, lakes, and rivers, and from my experiments, which show that even our modern plants can live in an atmosphere of nitrogen, but do not thrive in pure carbonic acid. I was thus led to the conclusion that the original atmosphere of our globe consisted of nitrogen alone, and that the oxygen of the atmosphere is the product of vege- table life (which must necessarily have preceded animal life). 1 The production of oxygen by the minute uni- cellular algae exposed to the light of the sun is a symbol of what took place in the primitive ages of the Earth. Carbonic acid must be looked upon as a volcanic pro- duct, extensively diffused through the Earth's strata, and into the atmosphere and waters. The primitive atmosphere of nitrogen would derive abundance of carbonic acid and vapour from volcanic action, which continued to be very intense long after the Coal flora period, and appears to have gradually diminished from that period to the present time, though it is still very active in many parts of the globe. Now let me say a few words on the dawn of animal life. 1 It might be objected that the plants which first produced atmos- pheric oxygen must already have contained oxygen as part of their tissues. Whence did they derive that oxygen ? But I have never said that plants were the creators of oxygen, only that they were the means by which Nature has placed free oxygen in the atmosphere of the Earlh. OXYGEN, PLANTS AND ANIMALS. 27 I have endeavoured to show that in the earliest ages of the Earth, when life first made its appearance, plants (anaerdbics) must have been formed long before animals (aerobics), since free oxygen was absent from the primi- tive atmosphere. My experiments on vegetation in hydrogen show that free hydrogen could not have existed in this primitive atmosphere any more than it can exist for any length of time in the atmospheric air of our days, without becoming oxidized, and converted into water. Nitrogen alone, on account of its inert nature, could have formed the Earth's atmosphere in the earliest ages of our planet's history ; and previous to the advent of life, this primitive atmosphere was charged with carbonic acid and vapour of water by volcanic action, such as we see manifested to a considerable extent at the present time. Hence, the earlier vegetative life of the globe de- veloped in an atmosphere devoid of free oxygen, con- sisting of nitrogen gas, with a certain admixture of carbonic acid and vapour, the whole of the oxygen now present in the air being due entirely to vegetation extending over immense periods of time. As the ancient plants were evidently anaerobic, it was very interesting to ascertain whether the plants of our present epoch were essentially of the same nature ; and my experiments have shown me that they are ; also, that they must have preceded animal life. Animal life has resulted naturally from the gradual transformation of anaerobic cells into aerobic cells, as a 28 THE EARTH'S ATMOSPHERE. consequence of the changing conditions, that is, the oxygen constantly poured into the air by vegetation. At what precise geological period oxygen became present in sufficient quantity to allow of animal life might appear an extremely interesting problem to solve ; but no such period witt ever be determined, because the change must have been exceedingly gradual, and the study of the lower forms of plant and animal life show us that there is no hard and fast line between the two kingdoms. There is no such thing to be discovered as " the first vestiges of animal life." As the oxygen evolved from the anaerobic cells became slowly and gradually a greater factor in the composition of the air, these cells had to accustom themselves to it, until some became more or less aerobic, and, finally, entirely so, and by their vital functions actually supplied carbonic acid to the air instead of oxygen. Between green plants, beings which are essentially anaerobic, and the more perfect animals, beings which are just as essentially aerobic, there exists a vast inter- mediate class which presents, more or less, the character- istics of both ; such are the various organized ferments, fungi and bacteria, etc., which represent the gradual transformation of the anaerobic cell into the aerobic cell, under the influence of the gradual change of medium; that is, the constantly-increasing amount of free oxygen in the atmosphere since the earlier geological ages. In the common yeast-fungus we have a familiar example of a cell which has undergone the influence of OXYGEN, PLANTS AND ANIMALS. 29 the change referred to a cell which combines the plant and animal properties, and secretes carbonic acid in the conditions in which the green unicellular algae secrete oxygen. In the latter case, the oxygen evolved is separated from carbonic acid, and the carbon retained by the plant ; in the former, carbonic acid is secreted by the yeast cell just as in the higher animals; the function is far more complicated, and requires a special nutriment, and the existence is rapid and short. The French naturalist, A. Dissard, has recently published a paper, La transpiration et la respiration chez les Batraciens (Comptes-rendus, Paris), which gives us some idea how the change in the medium determines a change of function, such as I allude to here. Kespira- tion is more active with aerial batrachians than in the aquatic species; exactly the reverse occurs for transpiration. In one of my experiments, in which a Convolvulus grew for fourteen weeks (25th July to 30th October 1893), the confined " primitive atmosphere " lost all its carbonic acid, and the atmosphere at the end of the experiment was richer in oxygen than is ordinary atmospheric air. This shows what would happen to the Earth's atmos- phere if there were an excessive supply of carbonic acid, and vegetation did not deteriorate : the oxygen of the air would increase year by year. In the present state of things ttiere is a kind of equilibrium apparent (not real), as during the last fifty or sixty years no great excess of oxygen gas has been detected by chemical analysis of the air, in whatever 30 THE EARTH'S ATMOSPHERE. locality, or at whatever elevation over the sea it may happen to have been collected. But what are fifty or sixty years compared to the thousands of centuries by which Nature counts her periods ! At Palermo it has been found that there is a slight diminution of oxygen in the air whilst the Sirocco blows. At Dresden, Professor Ficinus found a slight variation according to the direction of the wind ; with the west and south winds the quantity of oxygen was always the highest. Something similar has been noted with regard to air analyzed at Copenhagen, at Helsingfors, at Guadaloupe, and of the air over the North Sea. In spite of the utmost care in the analyses, there were considerable differences in the amount of oxygen found in all these cases. The air of Calcutta during an outbreak of Cholera in 1845 yielded only 20'35 of oxygen (instead of 21), and 0'13 of carbonic acid (instead of 0*04 or 0'05); and there are other examples tending to show that the volumetric proportion of 79 of nitrogen to 21 of oxygen is anything but a fixed quantity. However, I have little faith in the accuracy of these analyses ; and they must always be reduced to C. and 30 inches barometer, which some of them were not. In former years also, analysis of the air was very frequently performed with phosphorus, which gives extremely erroneous results unless special precautions are taken. In concluding the first part of this little work, we cannot help observing that it is a striking reflection when we consider that all the superiority of Man upon OXYGEN, PLANTS AND ANIMALS. 31 this Earth depends upon fire, and that this fire is got by oxygen, originally the product of the minute cells of such humble plants as the microscopic unicellular algae, vegetating under the mysterious agency of the Sun's rays ! Light, indeed, may be said to be the origin of Life. PART II. THE ATMOSPHEEE OF OTJR PRESENT PEEIOD. CHAPTER VI. The Atmosphere is only a Mixture of Gases, not a Compound Irrefragable Proof of this by Berzelius Its Changeable Composition The Inert Nature of Nitrogen Ammonia and Nitric Acid The Author's Experiments on their Mutual Conversion The Unexplained Phenomenon of " Nitrifica- tion" Its Universality Ammonia, like Carbonic Acid, a Volcanic Product Nitrification due to the Oxidation of Atmospheric Ammonia. THE ancients looked upon the air as an element, and I have shown that in the earliest ages of the globe it was really so, for the atmosphere must then have consisted of nitrogen only, and the free oxygen which now forms part of the air we breathe, and without which animal life is impossible, is entirely the product of plant life extending over countless ages. At the present time the atmosphere of the Earth, in accordance with the foregoing considerations, is not a compound, but a mixture of nitrogen and oxygen. This was amply proved by the great Swedish chemist, Berzelius, in his TraiU de Chimie (vol. i, p. 88, Belgian OF THF: UNIVERSITY CONSTITUENTS OF THE ATMOSPHERE. OF 33 edition). Here is the passage in question ; an important page in the history of science : " Some naturalists have endeavoured to prove that atmospheric air is an oxide of nitrogen. They base their opinion chiefly on the fact that it is almost exactly composed of four parts of nitrogen for one part of oxygen, and that consequently it contains half as much oxygen as nitric oxide gas. But if such were the case, atmospheric air would offer to us the first known example of a simple mixture having absolutely the same properties as a chemical combination of the same elements. For, in fact, an artificial mixture of four parts of nitrogen and one of oxygen does not differ from atmospheric air as to its physical and chemical properties ; and what proves clearly that this mixture is not a chemical compound is that no change in the volume, nor of the temperature, takes place at the moment the mixture is made. As, moreover, nitric oxide gas is converted into nitrous acid when it comes in contact with the air, it would result from this opinion that an oxide of a higher degree, and containing more oxygen, would possess the property of reducing, without the co-operation of any third body, an inferior degree of oxidation of the same radicle, a case of which Chemistry offers no example. Atmospheric air is, therefore, not a gaseous oxide of nitrogen, but a simple mixture of nitrogen and oxygen gases" This settled the question for ever. And it was this knowledge that our atmosphere is but a mixture, and c 34 THE EARTH'S ATMOSPHERE. not a compound, that has hitherto been an enigma in Science, ever since the fact was discovered. The more so that, neglecting to take into account that " time is the creation of Man," it was judged from a few analyses extending over a small number of years, that the proportion of oxygen and nitrogen in the air is invariable, and never has varied ! If only a mixture, and not a definite compound, how is it, people ask, that its composition remains fixed ? how is it that it shows the same quantities of oxygen and nitrogen in whatever part of the Earth it is analyzed, and at whatever height above the sea the sample of air is taken ? All this is explained, of course, by allusion to the law of diffusion of gases. But it must not be forgotten that changes in nature are very gradual, and very slow in com- parison with the short, rapid span of Man's existence. Several eminent men have already supposed, as we have seen, that the composition of the atmosphere is changeable. A slight practical glimpse of such a fact occurred in the analyses made by Levy, a Danish chemist, of air lying over the waters of the ocean between Havre and Copenhagen; and I myself made similar experiments with air taken at the surface of the sea many miles from the coast of Flanders. Such air contains somewhat less oxygen than that which is collected on the land. This was explained by the fact that oxygen gas is slightly more soluble in water than is nitrogen ; and free oxygen is required for the respira- tion of aquatic animals. CONSTITUENTS OF THE A TMOSPHERE. 35 The same slight deficiency of oxygen should be found in air lying over vast inland lakes ; for, the air ex- tracted from fresh water, by boiling, contains 33 per cent, of oxygen, instead of 21 (the proportion in atmos- pheric air). But the constant motion of the air keeps its composition very similar in all its parts, like that of a solution of sugar constantly stirred by a glass rod. Then, the nature of Nitrogen formed a subject of uncertainty. Here is a substance which, combined with oxygen, forms one of the strongest acids, and, combined with hydrogen, one of the most powerful alkalies. Now, other substances combine both with oxygen and hydrogen, but, as Berzelius remarks, always to form acids (Traite* de Chimie, vol. i. p. 146, Belgian edition). It is true that phosphorus and arsenic imitate nitrogen in this respect, but they form nothing com- parable for energy with nitric acid and ammonia. Berzelius did not perceive that nitrogen is essentially neutral, or inert ; that is why it must have formed the original atmosphere of the Earth. Hence, in nitric acid all the electro-negative properties of oxygen are ap- parent, and in ammonia all the electro-positive pro- perties of hydrogen. In neither case does the neutral nitrogen interfere. It is the only element of this ab- solutely neutral nature. Hence, also, all the compounds of nitrogen have to be formed indirectly, by round- about processes. We have no facts in the whole range of Chemistry more striking than that the two substances ammonia 36 THE EARTH'S ATMOSPHERE. and nitric acid, so essentially opposite in character, are readily convertible one into the other. I have found, for instance, that ammonia oxidized in the cold by a solution of permanganate of potash, forms nitrite and nitrate of potash ; and it has long been known that when zinc, or tin, is dissolved in nitric acid ammonia is found in the solution. For many years it has been supposed that the nitrogen of the atmosphere plays an important part in the process of "nitrification," and many theories have been put forth to explain it porous bodies, catalysis, electricity, bacteria, etc. but we may safely assert that it is still unexplained. In several experiments I made, years ago, with the view of thus forming saltpetre artificially, / never obtained any nitrates unless some ammonia-yielding sub- stance was present, and I look upon the phenomenon of nitrification as due to the slow oxidation of ammonia in nature. The process is universal ; it occurs constantly, everywhere ; but it is only in those parts of the globe where rain is scarce that the resultant nitrates are easily discovered, or where they effloresce from the soil. In all other places they are washed away by the rain as fast as they are produced, and find their way into the rivers. Now, ammonia is not only a volcanic product (like carbonic acid), but an organic residue a secretion that has found its way into the superficial strata of the Earth ever since life appeared upon the globe. Ammonia is a poison to plants, but nitrates are absorbed by all CONSTITUENTS OF THE ATMOSPHERE. 37 vegetables, and I have convinced myself that ammonia is converted into nitric acid before its nitrogen can enter the plant, and that ammonia will kill the plant unless this conversion can take place. In the earlier ages of the globe, there could have been no nitric acid, nor even ammonia ; but when the Earth had cooled sufficiently long before life appeared ammonia could exist in the volcanic products as it does at the present day, but no nitric acid. 1 Later still, nitric acid formed from ammonia (" nitrification ") was produced, and plant-life became possible. Ammonia, like carbonic acid, must therefore be looked upon as a volcanic product ; and, when organized beings decay, their nitrogen and carbon return to nature as ammonia and carbonic acid. Hence it is evident that atmospheric nitrogen takes no part in the important process of nitrification, unless it be that which is directly converted into nitric acid during combustion of various substances in the air, or by the lightning flash, and which may, after all, be due to the ammonia that is always present in the air. 1 Ammonia has recently been found in the mineral Apophyllite, to the extent of 0'03 to 0*5 per cent. CHAPTEE VII. Definition of the Atmosphere of the Present Day Transparency Spectral Lines of Oxygen not given by the Sun's Atmos- phere Observations and Experiments of Janssen, Piazzi- Smyth, Langley, Dewar, and Faraday. A POPULAR writer on Science has said : " The Earth we inhabit is surrounded by an atmosphere of air, the height of which is known to be at least forty-five miles. It presses upon the Earth with a weight equal, at the level of the sea, to about 15 Ibs. on every square inch of surface. As we ascend high mountains, this weight becomes less; as we go down into deep mines, it becomes sensibly greater. We breathe this atmos- pheric air, and without it we could not live many moments. It floats around the Earth, being in per- petual motion; and according to the swiftness with which it moves, it produces gentle breezes, high winds, or terrible tornadoes." It is hardly possible to give, in fewer words, a general definition of the Earth's atmosphere. The transparency of the air, cceteris paribus, must increase with the height above the Sea; but this increased transparency shows itself in a very remark- OBSERVATIONS. 39 able manner : the absence of some of the spectral lines of oxygen, when the Sun is viewed from the summit of Mont Blanc, has recently led the well-known French astronomer, M. Janssen, to the conclusion that there is probably no oxygen in the Sun's atmosphere. My friend, Piazzi-Smyth, when Astronomer-Eoyal for Scotland, was the first, many years ago, to carry an astronomical telescope into the higher regions of the atmosphere. With the view of avoiding the influence of a dense layer of air, he took his instrument to the top of the Peak of Teneriffe, where he made some very interesting physical and astronomical observations. These were, on his return to England, the occasion of the publication of one of the most curious and delightful books in our language (An Astronomer's Experiment, etc.). Since then, we have had a number of similar observa- tions by Professor S. P. Langley, of Washington, which have been carried out on the heights of the Californian mountains, in one of the districts of the globe where the atmosphere is extremely pure, and where he was provided with one of the finest telescopes ever con- structed. Under these most advantageous circum- stances, Mr. Langley made observations on the heat and colour of the sun and planets, the distribution of the lines of the spectrum, the constitution of the solar surface, the distribution of light and heat upon the disc, the extent of the absorbing power of the Sun's atmosphere, and that of our Earth, the temperature of the Sun (which he fixes at some degrees higher than 40 THE EARTH'S ATMOSPHERE. the fusion point of platinum), and many other important researches, to which we need not here refer. I should mention, also, the recent curious experi- ments made by Professor Dewar, of the Eoyal Institu- tion, on the liquefaction of oxygen gas and of atmospheric air, accomplished by the application of intense cold and pressure. In following up the experiments of Pictet and others in this direction, our English professor has gone a step further (Chemical News, 19th January 1894), and his results have excited general interest. Berzelius recognized that the true colour of atmospheric air is blue, and the liquefied oxygen of Professor Dewar is likewise blue. It possesses the most singular properties, being without any action upon such inflammable metals as potassium and sodium, which shows what an enormous influence is exerted by temperature on chemical action. This became evident, years ago, in experiments by the celebrated Faraday 1 as regards liquefied gases. He found that liquefied protoxide of nitrogen would not act on potassium, nor liquefied chlorine on antimony, etc. 1 See Dumas, filoge de Faraday, p. 12. CHAPTER VIII. Sulphur always present in the Atmosphere Characin, the Cause of the Odour of Marshy Air Odours of the Air in Different Countries The Odour of the Sea-Air Detected by the Author in Marine Fossils of the Tertiary Period Odour of the Air after a Summer Shower Observations regarding Ozone. PUKE air is odourless and tasteless, except when ozone is strongly developed, or when lightning strikes an object on the surface of the Earth. In the latter case, an odour of sulphurous acid is distinctly noticed, as I have had occasion to observe more than once. On one of these occasions, in Paris in 1858, it affected the neighbourhood for a considerable distance around, and penetrated all the houses. This odour of sulphurous acid is likewise perceived at sea when a ship is struck by lightning. It proves the existence of a certain amount of sulphur, or some compound of sulphur, in the air, even hundreds of miles from land. That sulphur, in some form, is a constant constituent of the Earth's atmosphere appears to be becoming less doubtful every day. In the early part of this century a writer in the Archiven der Pharmacie, named Dulk, 42 THE EARTH'S ATMOSPHERE. reported that after a storm of thunder and lightning which broke over Osterrode, in Prussia, on the 22nd April 1836, a yellow powder was found in the water collected from two streams. It was formed of coarse grains, like small hailstones, some of which were nearly as large as peas, and these formed semi-transparent drops, which were fragile, and could be easily broken between the fingers. Afterwards, the grains became a darker yellow, and harder ; so that they could no longer be broken by pressure between the fingers. It was proved that these yellow grains were sulphur, much purer than the ordinary brimstone of trade. Mr. Dulk, and his friend Mr. Lange, then requested the Mayor of Osterrode to enquire of the proprietors of the streams what had happened. The latter, and their servants, all declared that there had been no sulphur before the storm, and that after the storm, sulphur had not only been found in the two streams, but in the gutters, and empty vessels, such as saucepans and tubs, belonging to artisans in the neighbourhood. The so-called " sulphur rain " due to the pollen of the Pine trees, often observed in Norway and Sweden, has been occasionally witnessed also at Oleron in the Basses Pyrenees (France). Another cause of odour in the air, extending over wide districts of marshy lands, is due to the volatile substance characin, which I discovered in 1879. 1 It forms very thin iridescent films on the surface of stag- nant waters where algae abound, and on the water of 1 Chemical News, London, 1879. ODOUR OF THE ATMOSPHERE. 43 tanks in which these microscopic plants are cultivated. It is soluble in alcohol and ether, and is volatile, it possesses the characteristic odour of marshy air, so intense during hot summer weather in the flat districts of Flanders, especially along the wide ditches which border the Chaussfos, where I first noticed it. It has the odour of the Cham, hence the name I gave it, and to most persons is very disagreeable (botanists call one of the species Chara fcetida) ; but all fresh water Algoe produce it, Conferva, Palmella, Oscillaria, etc. ; and it is often to be noticed, during hot weather, in glass tumblers which have been wiped out with a towel on which microscopic Algce have developed, through want of cleanliness, and neglect of soaking the glass-towels in boiling water. Characin may, of course, be produced by the influence of microbes, but it is quite distinct from them, being a well-defined substance, approaching to the nature of camphor. I have noticed, during my travels in Europe, that on passing from one country to another, a different odour is perceptible in the atmosphere. If we take the boat to Ostend, for instance, we are at once struck, on arriving, by the peculiar odour in the air ; and the traveller who proceeds from Belgium to France, from France to Germany, etc., can scarcely fail to notice the peculiar change in the odour of the air when he changes his abode to reside in another country. The cause of this must be looked for in the various modes of life of the inhabitants, and has little to do with the natural constituents of the atmosphere. But even a journey 44 THE EARTH'S ATMOSPHERE. from an inland region to the sea-coast makes us aware of what is commonly called the " odour of the sea," which was noticed as early as the days of Alexander the Great; for the old author, Quintus Curtius Eufus, distinctly informs us that the soldiers of Alexander knew when they approached the sea by the odour it diffused in the air " agnoscere se auram maris" Now, I have found that the fossil marine worms (Teredo), which I used often to obtain from the tertiary sands of Brussels, gave a distinct odour of the sea (aura maris\ when broken with a hammer, or scratched with a knife, shortly after being taken from the strata in which they have been imbedded for myriads of cen- turies. 1 This is infinitely more astonishing than the accounts of the extraordinary persistency of the odour of a grain of musk diffused through the atmosphere of a large room for a great number of years. Travelling on foot in Germany, I was often able, dur- ing the night as well as by day, to distinguish when I was approaching a beech forest or a pine forest, by the different odour diffused through the air by each of these trees. All these facts show that the lower regions of the air become impregnated with various volatile substances which are constantly produced on the Earth's surface, and the most minute quantities of which affect the delicate tissue of the sensitive olf active nerves. I need 1 Phipson, " Note sur les Teredo fossiles," in the Comptes-rwidus of the Paris Academy of Sciences, 1857. ODOUR OF THE ATMOSPHERE. 45 not develop this subject further; but there is one observation 1 desire particularly to allude to, namely, the very delicious odour perceived in the air of a country garden after a heavy summer shower. For many years the cause of this odour escaped me com- pletely until, one day in 1863, I found that certain specimens of chalk taken in the open country of Picardy, in France, developed a similar fragrance when they were dissolved in diluted hydrochloric acid. For a long time I was unable to trap the odoriferous sub- stance which thus escaped with the carbonic acid ; but finally I succeeded by passing the gas given off by the chalk through a solution of bromine in water. The bromine compound thus obtained was found to be analo- gous to bromo-cedren, showing that the odour was due to some essence like that of cedar. Hence, I was led to conclude that the pleasant fragrance diffused through the air in a country flower-garden after a heavy shower of rain, is due to the displacement by the rain of the flower-essences (essential oils) absorbed by the dry porous soil during the hot days of summer. Many years afterwards a well-known chemist in Paris made some experiments, which fully confirmed my views in this respect (Chem. News, Lond. 1891). So much has been written upon the peculiar state of oxygen known as ozone, that my remarks on this subject must be very brief. 1 With us in England, I find it 1 Phipson, " La Force Catalytique,"etc. (Soc. Holl. desSc., Haarlem, 1858). See also the same author's papers in the Chemical News, London, from 1860 to the present time. 46 THE EARTH'S ATMOSPHERE. occurs chiefly with westerly winds blowing direct from the Atlantic, and is very perceptible on going into the open air after being for some time in the close atmos- phere of a room. Those who wish to know what this odour in the atmosphere is like, should place a stick of phosphorus in some water contained in a large glass globe, in such a manner that about half the phosphorus stands above the water. In the course of a few hours the air of the glass globe will have a very strong odour of ozone, and will act upon a strip of paper steeped in starch with a little iodide of potassium, turning it blue. The presence of ozone in the atmosphere of any given locality renders the air highly tonic, bracing, and anti- septic. It is rarely present in the atmosphere of densely populated districts, except when a westerly gale is blow- ing, as it is readily destroyed by the effluvia of animal life, and in presence of organic matter prone to oxidation, or in a state of decay. It is often present in sea-air. Some experiments which I published long ago (loc. cit.) have proved that whenever the atmosphere acts upon an organic substance, such for instance as a slice of apple, which it turns brown, the oxygen is immediately trans- formed into ozone (called by some "nascent oxygen," because when oxygen leaves a compound it is in the same state). Again, ozone formed in an atmosphere at a very low temperature such as is met with in the Arctic regions, is liable to affect the flesh of animals exposed to it before being cooked, inducing all the effects of putre- ODOUR OF THE ATMOSPHERE. 47 faction, as was observed by the young and ardent explorer Dr. Kane in the famous Grinnell Expedition in search of Sir John Franklin. 1 1 Phipson, " Sur la putrefaction a 35 sous zero," in the Comptcs- rendus of the Paris Academy, 1859. CHAPTER IX. The Electric Phenomena of the Atmosphere The Author's Re- searches and History of Electric Discoveries Phosphorescence of the Air Vibratory Nature of the Lightning-flash. THE electric phenomena of the atmosphere have always been a source of the greatest interest, and the discovery of the nature of lightning by Benjamin Franklin was one of the greatest achievements of the last; century. A history of Atmospheric Electricity is given in one of my former works, 1 where I have traced the progress of this important branch of physical science from its birth to the present epoch, giving an account of Franklin's celebrated kite experiment and what led up to it. Long electric sparks had been obtained from the extremities of isolated metallic rods, raised high in the air, by Dalibard in France, some months before Franklin made his experiment ; but it was at the sug- gestion of the latter. Such experiments are very dangerous, and the young Professor Eichmann was killed in this way at St. Petersburg. It is not necessary that storm-clouds should be present, for if an isolated condenser be suddenly 1 Familiar Letters on some Mysteries of Nature, London, 1876. ELECTRIC IT Y PHOSPHORESCENCE. 49 launched into the air at any time, strong currents of electricity (usually positive) are obtained. This experi- ment, which I performed for the first time in company with William Thomson (now Lord Kelvin), many years ago, at the Philosophical Institution in Glasgow, was merely an extension of the ingenious experiments of Benedict de Saussure (1767), made in the Alps with his electroscope : x whenever he raised the little instru- ment above his head, the pith-balls separated, showing that the electric tension of the atmosphere increases with the height above the ground, and is generally positive. M. Ch. Andre 2 concludes from observations, made in a balloon, on the variation of the electric state of the higher regions of the air, that in fine weather the electric tension certainly does not increase with the altitude ; but he does not appear to be entirely satisfied, at present, with these observations, and hopes to repeat them. During a thunderstorm, this tension will change its sign many times, often, in fact, with every flash of lightning. In the experiment just alluded to, the isolated condenser, communicating by a long wire with Thomson's galvanometer-electroscope upon the table, was attached to a long pole : when this was thrust suddenly out of a window to a great height in the air, the needle of the galvanometer was immediately set in violent motion. 1 Benedict de Saussure, Voyages dans les Alpes, 4 vcls., 1779-1796. ' 2 Ch. Andre in the Comptes-rendus of the Paris Academy, 27th -November 1893. D So THE EARTH'S A TMOSPHERE. In recent times Mr. M'Adie has succeeded in getting electric sparks from a kite raised in the air when there were no clouds in the sky. In August 1894, four soldiers were struck down, and severely injured, in presence of the Duke and Duchess of Connaught, at Aldershot, by a flash of lightning that destroyed a captive balloon to which they were attending. The day was characterized by a series of small thunder- showers of short duration. In dry summer weather, the dust raised by the French postilions in Languedoc, during the afternoon, has been known to remain suspended in the air the whole of the night, on account of its electric state. That this electricity is due to the friction of the horses' feet, may be demonstrated by throwing a little fine dry sand upon the condenser of a galvanometer-electroscope, and blowing it off again ; in each case the needle of the instrument is vividly deflected. I have described, in my work above mentioned, a number of wonderful phenomena due to atmospheric electricity, such as the emission of light from the hats, and raised hands, of travellers on the summit of a mountain, the buzzing noise emitted by their Alpen- stocks when thrust into the soil, which has been com- pared to that of a boiling kettle ; the marvellous field- lightning of the Jura which, during electric disturbance of the air, plays over the pastures on the slopes of the mountains, and has also been witnessed in Mongolia. There, also, I have recorded the history of the discovery of lightning conductors by Benjamin Franklin (1749- / [UNIVERSITY } ELECTRICITY PHOSPHORESCENCE 51 1752), and the discovery, a few years Thomas Eonayne, of London, concerning the electric nature of fogs (1761), a subject since investigated by Peltier and others. An electrometer thrust into a dense London fog often shows enough electricity to send a telegram round the globe; and, in 1876, I published the fol- lowing lines: "If after ascertaining the nature (or sign) of this electricity, the fog could be supplied with a plentiful amount of opposite electricity, I have no doubt that it would be entirely dispersed in the course of a short time/' l Independently of the beautiful phenomena pro- duced by the Aurora borealis in the highly rarefied regions of the atmosphere, I should notice here those gleams and flashes of light, probably of an electric nature, which I witnessed accompanying the remark- able swarm of shooting stars in November 13-14, 1866, and which were noticed by others in the star-shower seen the following year in the West Indies. An account of this phenomenon was given in my note to the Academy of Sciences at Paris in 1868. 2 The phosphorescence of the air, which allows a traveller on the darkest nights, when there is no moon above the horizon, to find his way in the open country, and the phosphoric shining of .isolated masses of cloud, often noticed, and described in my little 1 Phipson, Familiar Letters, etc., p. 37. 2 "Sur les phenomenes lumineux qui accompagnent les essaima d'etoiles filantes " (in the Comptes-rendus, Paris, 1868). 52 THE EARTH'S ATMOSPHERE. volume on Phosphorescence published in 1862 (my first work in the English language), must doubtless, as Humboldt suggested, be connected with the con- stantly varying electric state of the higher regions of the Earths atmosphere. These phenomena, which were known to the Italian philosopher, Beccaria, in the middle of the eighteenth century, have been often witnessed by me. I should also mention the phosphorescence of the snow and ice on the glaciers of the Alps: the darker the night the more brilliant is this effect, so that it appears sometimes like a second sunset. The snow which lies in the valleys of Piedmont, Switzerland, Valais, etc., is likewise affected in the same way; the bluish light emitted in these cases is due to phosphorescence ly insolation. It is not remarked on snow which has fallen shortly before night, and which, consequently, has not been long exposed to the sun. Although Franklin and his successors have per- fectly demonstrated the identity of lightning and the electric spark suspected years before by Otto von Guericke and Dr. Watt yet the exact cause of the light that flashes through the atmosphere, and of its tiny representative which rushes between the poles of an electric battery, is quite unknown. By modifying the medium, we modify the spark; so that in highly rarefied air, for instance, it takes the appearances of the Aurora borealis. What is the cause of the sudden light which issues from the storm-cloud, or through the air how is that light produced ? ELECTRICITY PHOSPHORESCENCE. 5 3 Some writers have imagined that lightning was due to the combustion of hydrogen gas, supposed to exist in the higher regions of our atmosphere ; or to that of carburetted hydrogen (marsh gas) which has really been detected on several occasions in the air ; or, again, to that of nitrogen, as in the celebrated experi- ments of Cavendish, who obtained nitric acid by passing electric sparks through atmospheric air. Nitric acid is, indeed, present, in minute quantities, in storm rain, and I am of opinion that all rain likewise con- tains it. My own idea is that lightning is due to a vibration of the air similar to what occurs in the little instru- ment known as the briquet a air, where sudden compression of the air in a cylinder by a blow upon the piston will cause it to ignite a piece of tinder. A similar vibration of the air is caused by the rupture of the extremity of a Prince Eupert drop, which causes a sudden light, and by the discharge of an air-gun, also by the rupture of a glass vessel exhausted of air. Similar vibrations, producing light, occur when crystals form in liquids, or by cooling after fusion, or by sublimation, or when divided suddenly by cleavage phenomena which I have witnessed scores of times. 1 So that the minutest molecular vibration is capable of yielding a sudden flash of light. The close calm weather which often precedes thunder- 1 Phipson, Phosphorescence, or the Emission of Light by Minerals, etc., 1 vol., London, 1862. 54 THE EARTH'S ATMOSPHERE. storms in our temperate climate, is accompanied by an increase in the various odours perceived in the air. The perfume of flowers is very much stronger for awhile; and, in country places, it is not unusual to perceive, at such times, the disagreeable odour of cess-pools all over the district a fact which clearly - points to the necessity of a more perfect system of drainage and disinfection in our country homes. CHAPTEE X. An Unexplained Condition of the Atmosphere Effects of Glare Snow-blindness Hemeralopia and Amaurosis. THERE is a certain, hitherto unexplained, condition of the atmosphere, which usually lasts for a few hours at a time, and rarely more than one day, or, perhaps, two days. During this condition the optic nerves of men and animals are painfully affected. I allude to what is commonly called " glare," not unfrequently perceived at the seaside, and often when the sun is not shining brilliantly, but is hidden by thin cloud, or haze. The existence of this painful "glare," even when the sun is dimmed, is a subject which has not been fully studied. I feel convinced that we have in the solar spectrum, besides the rays of light and heat, and the actinic, or chemical rays, others which specially affect the nervous system in the higher animals, and which appear to act also on those 'lower forms of life, in some of which no traces of a nervous system have, as yet, been discovered. This peculiar condition of the atmosphere affects some people more than others. Many are obliged to wear coloured glasses 56 THE EARTH* S ATMOSPHERE. in order to avoid its effects, or to pull dowu the brim of their felt hats to a level with the lower eyelids, as they do at Naples. Snow-blindness is supposed to be occasioned by the vivid reflection of the solar light from the white mantle of the brilliant white crystals which covers the ground, and more or less complete amaurosis is produced, especially in aged persons, by the bright solar radiation on the sea-coast, or by the light from brilliant white houses in inland cities. One of the most remarkable cases of snow-blindness ever reported is that by the late General Miller, in the Edinburgh New Philosophical Journal (1835) : A division marching from Cuzco to Puno, in Peru, halted at Santa Kosa. During the night, snow fell abundantly, nevertheless the march was continued next day, when, with few exceptions, the whole of the soldiers were attacked with sore eyes, " due to a disease called by the natives norumpi. It produces almost total blindness for some time, and great pain. There is also delirium of a peculiar kind, and it is often fatal. The division in question lost one hundred men in fifteen hours from this affection. The disease generally lasts two days." Dr. August Berlin, of Stockholm, has proposed a new theory for snow-blindness. He went on an expedition to Greenland in 1883, during which he had ample opportunities for observing it. The geographical distribution of the affection closely follows the isothermal lines in the three continents GLARE AND EYESIGHT. 57 bordering on the North Pole ; it comes further south in America and Asia than it does in Europe. It is- also met with in very elevated regions, even under the tropics. In the temperate zone it occurs occasionally, but in a milder form. Its cause, according to Dr. Berlin, resides in great dryness of the air, and intensity of the solar rays. To prevent snow-blindness the Esquimaux use a disk of thin wood with a minute transverse slit in the centre. They call these wooden spectacles their " snow- eyes." Instead of this, goggles made of moderately fine wire network, without glass, have been recom- mended. Medical men class these atmospheric effects upon the optic nerve under the term of hemeralopia (or " night- blindness," because they are chiefly observed at night). It is not uncommon that a considerable number of soldiers become thus completely blind during the night, and recover their sight again at daybreak. The com- plaint comes on periodically every evening, and may last for a fortnight, or even for a whole month, when it disappears without leaving any traces. The army surgeon, Dr. Better, saw sixty of his men struck down in this way at Wissembourg, just before the Franco -Prussian war ; and the troops in garrison at Strassburg suffered in a similar manner. Generally speaking it is cured, in mild cases, by keeping the men in the dark for two or three hours; or, sometimes, for twelve hours. In 1891, Dr. Schirmer endeavoured to explain this extraordinary atmospheric effect upon the 58 THE EARTH'S ATMOSPHERE. eyes, by reporting it to an action upon the pigment- cells of the retina. But it still remains a mystery. That same year Dr. Venneman described an " epidemic " of hemeralopia which he observed in the neighbourhood of Louvain (Belgium). Forty-two cases of this peculiar affection came under his observation, and embraced all classes of people, children being more generally affected than adults. Fever, with headache, preceded the affec- tion of the eyes, and lasted for two or three days. With the appearance of these symptoms the ophthalmo- scope revealed a slight retinal oedema about the disc, especially along the course of the vessels, with diffuse streaks and markings of black pigment. When normal vision returned these appearances gradually vanished. It is, therefore, an atmospheric effect upon the retina, or optic nerve; but no one has yet been able to determine in what consists the special condition of our atmosphere which produces these curious and painful effects. So little does the last-named physician suspect the real cause, that he looks upon the cases at Louvain as an epidemic, similar to influenza, confusing it with the amaurosis so often noticed, of late years, after attacks of that disease. CHAPTEE XL Solid Substances in the Atmosphere which fall upon the Earth, or can be detected in suspension in the Air The Author's first Discovery of Iron Particles in the Air, after the Meteor Stream of November 1866 Confirmed by other Observers His detection of Fossil Bacteria in the Air ; and of minute Crystals of Ice His Observation of Bundles of Grass trans- ported for hundreds of miles A Similar Case observed by Boussingault Presence of Salt and Sulphate of Soda in the Air Gossamer Birds and Insects Cosmic Dust Ex- plosion of Meteors Periodic Plants Transportation of Frogs, Stones, Volcanic Ash, etc. List of Extraneous Sub- stances Mode of collecting Bacteria Observations by Pasteur, Miguel, and the Author. As early as 1854, I examined a singular mucilaginous substance mentioned by Mulder and Berzelius under the name of "Mucilage atmosphdrique" It is found lying in the low Flemish pasture lands in the neigh- bourhood of stagnant pools, and the peasants of the Netherlands believed it to be dropped by shooting- stars, since it is occasionally seen at ight to be phos- phorescent. I shall never forget the youthful ardour with which I went through the early morning mist in search of this mysterious atmospheric mucilage, trudging over the damp fields which surrounded my 60 THE EARTH'S ATMOSPHERE. father's house in the neighbourhood of Brussels, and scattering hundreds of large blue crows, which rose, on my approach, from the edges of the shallow patches of stagnant water. On careful examination it was found to be frog-spawn, which had been swallowed and then voided by the immense blue crows which are so numerous in those districts. In connection with this curious subject I have since found that in Donovan's British Birds (1794, vol. iv., plate 77, the Winter Gull) he says : " Mr. Pennant observes that the gelatinous substance known by the name of Star spot, or Star jelly, owes its origin to this bird, or some of the kind, being nothing but the half- digested remains of earth-worms on which these birds feed, and often disgorge from their stomachs/' The Winter Gull (Larus hybernus) is a common bird in England, and frequents inland rivers, fens, and moist meadows, hundreds of miles from the sea, in winter time ; hence its name. Its general colour is white, with a few brown spots on the wings, etc. Mr. Morton, in the Natural History of Northampton- shire, says : " In the course of my correspondence with J. Platt, of Oxford, I recollect his having mentioned that once meeting with a lump of this Star jelly, on ex- amining it he found the toes of a frog or toad still adhering and undissolved, and from thence he con- cluded it to be the remains of one of these having been swallowed whole ~by some bird, and the indigestible parts brought up in the condition he found it." About the same period, when prosecuting my studies FALLS OF FOREIGN BODIES. 61 at the University of Brussels, I was called upon to make a chemical analysis of the dust collected by one of my professors from the air of houses in that city. I found that it consisted almost entirely of organic matter, leaving only a minute quantity of ash when burnt, in which soda appeared to be the principal ingredient. Many years later, at the commencement of winter, I examined the first fall of snow in the neighbourhood of London, and found it teeming with organic germs and unicellular Algce. In 1866, shortly after the celebrated star-shower of November, described in one of my former works, 1 I exposed to a south-westerly gale, plates of glass covered with glycerine, which were afterwards ex- amined under the microscope, and revealed some black specks which contained iron, and gave yellow chloride of iron by treatment with hydrochloric acid. This was the first experiment of the Jcind ever made, and is recorded in my book. Since then this observation has been confirmed by Cunningham, Tissandier, and others, who have all found iron, probably of cosmic origin, floating in the atmosphere of our Earth. Ten years previously I had used the same device (with solution of gum instead of glycerine), both in France and in Belgium, for collecting substances carried through the air by the wind ; and among other curious 1 Phipson, Meteors, Aerolites, and Falling Stars, London, 1867. The description is an Appendix, as the work was written long before that famous star-shower occurred. 62 THE EARTH'S ATMOSPHERE. objects thus collected I have met with the microscopic hairs (pili) of certain Alpine plants, flourishing hundreds of miles from the spot where the experi- ment was made. I have more recently collected in this manner ex- tremely minute circular cells, which resisted a red heat in contact with the air, and were found to consist chiefly of silica. They appeared to be, in fact, fossil bacteria, 1 It also fell to my lot, in my student days, to place beyond doubt the existence of crystals of ice in the atmosphere minute crystals of ice suspended in the air, which are the cause of the phenomena known as Solar and Lunar halos : One night during the spring of 1855, a magnificent halo of 22 degrees encircled the moon as seen at Brussels. It is generally admitted that these halos portend " rain within twenty-four hours," which is explained by a change of wind a warm southerly current mixing with the air in the higher regions charged with ice-crystals, and bringing down the latter as rain. On this particular occasion things occurred in a rather different manner; for, the following morning as I was proceeding to the University for the early Chemical Course at eight o'clock, I found the air full of minute floating crystals which glittered in the bright sunshine like myriads of small diamonds. It was a most curious sight, and one never to be forgotten. The tiny crystals fell all the morning, covering objects on 1 Phipson, "Grains of Silica and Micrococci in the Atmosphere," published in the Chemical Neivs, 1881. FALLS OF FOREIGN BODIES. 63 the Earth's surface with a thin layer resembling hoar- frost, and finally changed to rain during the afternoon. Here is another curious observation which I find among my notes. Standing one morning during the month of June 1861, on the banks of the Eiver Thames, near London, I was a witness of the following singular spectacle : The day was calm, with only a slight westerly breeze, there was bright sunshine, and the sky was blue. Suddenly there appeared moving specks in the atmos- phere to the west of the spot on which I stood, and evidently at an enormous distance. They were like a very distant flight of birds ; but they got much larger than any birds, as they approached. At last some of them began to fall into the river near Putney bridge \ and two or three of these curious objects fell into my father's garden. On examination, they were found to be recently cut grass, twisted into circular masses, much- larger than a man's head. I knew that no grass had been cut for hay within hundreds of miles of my residence, and I at once assimilated this phenomenon to the falling of volcanic ash upon ships far out at sea,, and hundreds of miles from any volcanoes, of which instances have occasionally been put on record. Many years afterwards, I found that a precisely similar phenomenon had been witnessed by the celebrated Boussingault at Caracas, in Venezuela, and is mentioned in the second volume of Humboldt's Views of Nature. M. Boussingault, who was then Professor at the 64 THE EARTH* S ATMOSPHERE. School of Mines at Santa-Fe de Bogota, whilst climbing the hills of Caracas, witnessed in the middle of the day, during an excursion to the summit of Mount Silla, a phenomenon which appeared to prove in a striking manner the existence of ascending currents of air. He, and his companion, Don Mariano de Eivero, saw numbers of white, shining bodies rise from the Valley of Caracas, and reach the summit of Mount Silla, 5400 feet high, whence they fell on the opposite slope. This phenomenon lasted for an entire hour, without any interruption. At first, M. Boussingault imagined it was a flight of birds, but he was soon able to convince himself that these bodies floating in the air were small, round bundles of grass, chiefly composed of the species Aira tenacissima, which is plentifully mixed with Agrostis grass of the valleys of Caracas and Cumana. 1 The account of the phenomenon witnessed by me was published in the Comptes-rendus of the Paris Academy 2 before I knew of Boussingault's observation. The presence of salt (chloride of sodium) in the air of the sea-coast, especially when a brisk breeze plays upon the spray of the waves, is a matter of common experience. But it is not so generally known that -another sodium salt, namely, sulphate of soda, in the solid state, appears to be constantly present in the atmos- phere, at least in the lower regions. A supersaturated solution of sulphate of soda 1 Humboldt, Tableaux de la Nature, vol. ii. p. 37. 2 Phipson, " Sur une pluie de foin," in the Comptes-rendus, Paris, 1861. FALLS OF FOREIGN BODIES. 65 crystallises immediately the bottle containing it is opened, in whatever place the observation may happen to be made, whilst solutions, equally saturated, of other salts do not present the same phenomenon. This fact, which has been brought to light by F. Parmentier and M. Margueritte, 1 appears to prove most conclusively that sulphate of soda must be constantly present in the lower regions of the atmosphere, and this salt being universally suspended in the air, supplies the necessary microscopic nucleus-crystal, which causes the whole solution to solidify the moment the bottle is opened. It has long been known that butterflies and other insects are occasionally transported, by aerial currents, from the valleys to the summits of the highest moun- tains, and far out to sea; and the spiders' webs which are found floating in the air (generally, with us, in October, though I have seen them also in March, both at St. Cloud, near Paris, and in the South of England), are alluded to by many of our poets as "gossamer." In this respect I shall never forget a journey I once made, in October, from Paris to Brussels, by the line then recently constructed through Erquelinnes. On alighting at the station of Erquelinnes, I noticed that the funnel of the engine was covered with these spiders' webs, and appeared just as if it had be^en wrapped in a silk shawl several inches thick. The description of the particular species of spider that migrates in this manner by the currents of the atmosphere is given by Kirby 1 Comptes-rcndus of the Paris Academy, 1889. 66 THE EARTH'S ATMOSPHERE. and Spence in their great work on Entomology. I have since seen it rise in the air, like a fly, from the summit of plants in my garden at Putney, in September, by means of its invisible thread. Doubtless, the migration of birds is aided in a similar manner by currents of air. Our swallows usually appear in great numbers after a stiff gale has been blowing for many hours. It is difficult, however, to account for the manner in which the minute red spiders, known as social mites, are transported through the air. Suddenly, some fine morning, they will be found clustering by thousands, on nails, or other prominent objects, at the top of gates, or fencing, disappearing, in a few days, as mysteriously as they came. This singular occurrence has been sometimes witnessed in Putney and other westerly quarters of London. In another place, I have given numerous instances of what is supposed to be Cosmic dust?- as distinguished from the better known dust, or ashes, due to volcanic eruptions, such as those of Krakatoa which, not very long ago, diffused into the atmosphere immense quanti- ties of volcanic ash that remained suspended in the atmosphere for several years, producing the most gorgeous effects of sunset for two or three years in succession. It is very probable that fine sunsets of a less remarkable kind are often due to a similar cause. The whole subject of Cosmic dust, and other sub- 1 Phipson, Meteors, Aerolites, and Falling Stars, 1 vol., London, 1867. FALLS OF FOREIGN BODIES. 67 stances observed to fall from the atmosphere, has been discussed in Chapters XIII. and XVII. of my work just alluded to. The late learned Baron von Eeichenbach long ago collected virgin soil from the summits of mountains in Germany, and found it con- tained traces of nickel, a metal invariably present in aerolites. I did the same, in Waldeck, in 1865, tak- ing the earth from places where human industry had not yet penetrated, and with similar results, which shows that meteoric dust, the produce of meteors, finds its way through the air to the surface of the Earth. Professor Nordenskiold asserts that he has, also, collected meteoric dust in the snows and ice of the Arctic regions. But all these observations require more careful discussion than they have yet received, and so does that one published by Mr. Baumhauer, who found iron pyrites enclosed in hailstones which fell in Holland. 1 The cause of the explosion of a meteor in the Earth's atmosphere is due to the sudden rise of temperature on the surface (which is thereby fused, whilst the interior is most intensely cold), by the friction with the air through which it rushes. It has been estimated that if the speed of a meteor is only slackened by j<^ long time. / Rising N. winds of short dura- rapidly. tion. Wind goes again S.W. and the baro- meter falls again ; generally not so low as W. , before. f With falling ther- Rain almost certain. mometer. Without an im- E. or N.E. wind; sky mediate fall of charged with cloud ; , Rising. \ the thermo- raii>, snow, or fog. But meter. the weather gets fine, and cold if E. wind continues. Rain. The thermometer falls ; wind goes N.W. ; rain persists, and in winter becomes snow. i$o THE EARTH'S ATMOSPHERE. IMMEDIATE WEATHER continued. Direction of wind. State of the barometer. State of the sky. Weather to be expected. Rising. Snow. Cold. If the N.W. wind brings more snow the cold increases and becomes severe. Rising slowly. Oscillating. Constancy of N. winds. Scuddy, changeable m weather. W. Falling. Weather gets warmer ; rarely rain is immedi- ate, but falls as the rotation of the wind is re-established. Falling very Abundant rain. Gale from the S.W. low. , Uncertain, or Clear sky, cold. fine weather. Rain or snow. Wind goes N. or N.E. ; showers and sunshine ; blue sky between the Rising. 4 Snow, after other showers. Cold ; which will be snow from W. severe. N.W.! Wind very strong Cold ; wind goes N.E. after a gale, thermometer Falling. falling briskly. Milder interval without rain, until the baro- meter rises and the wind goes round ; at this moment rain falls. This table, which was drawn up by Houzeau, first assistant to the celebrated Qnetelet, director of the Brussels Observatory, has been tested by me on many occasions in Belgium, France, and Great Britain ; it has proved generally correct for the first two countries, and WEATHER. 151 tolerably so for England, where the weather is more changeable, and at the same time more temperate, than in other parts of Europe. Nevertheless, it is only an indication of probable results; it contains nothing absolutely certain. It is now almost a century since our great English meteorologist, Howard, turned his attention to the amount of rain which falls in a given locality and at a given season. Speaking of England, some have said that April is the driest month, and October the wettest ; but Fitz-Koy says March and July. Howard showed, long ago, that the quantity of rain which falls in London in one year is very variable : In 1802 he found 14 inches; in 1810, 27|; and in 1816, 32 inches. Symons puts the mean rainfall per annum for London at %5 inches, and for all England at 31 inches. The proportion for the various seasons is roughly stated as : Winter 5*8; Spring 4'8 ; Summer 67; Autumn 7*4; total = 24*8 inches. But averages (or means) are only useful for comparison. Engineers require to know the extremes', for these are what are actually experienced, and what we have to deal with in practice. For in- stance, more rain may fall in an hour than is due to one month, according to averages. If the flow of water in our rivers during a dry season is taken as unity (one volume), the volume in wet weather is generally 300, and in extreme cases 500. A river in England may rise, from floods caused by rain, as much as 23 vertical feet; and in South Africa, and America, 152 THE EARTH'S ATMOSPHERE. etc., as much as 60 or 70 feet. As regards waterworks, we must know the minimum ; for bridges, culverts, and embankments, the maximum of water which the atmos- phere will yield in a given locality. It is not generally known that the rainfall of all towns in Great Britain is more than sufficient, if it were collected, to supply all the wants of their inhabi- tants as far as water is concerned. CHAPTEK XXIII. Fogs and Electricity Konayne's Discovery Luminous Fogs Prevention of Thunderstorms and Hail. THOUSANDS of tons of water are evaporated daily from the waters of the ocean by the heat of the sun's rays ; this water rises as vapour into the air, forms clouds, fogs, and dew; falls again as rain, produces springs, streams, and rivers, which flow to the sea, and whilst protecting the surface of the Earth from the effects of undue radiation, gives to the soil that degree of moisture which is essential to life and fertility. Fogs, in the days of Sir Humphry Davy, were thought to be always due to the cooling of the air lying over water ; and, no doubt, a mist is often formed from this cause ; but that is not invariably the case. George Harvey, in 1823, contradicted Davy's statement, and showed that fogs were sometimes formed when the temperature of the air on the land is higher than that of the water and the air above it, ir> which the fog exists. As early as 1814 five years before Davy's observation Thomas Young showed, on the occasion of a remarkable fog which lasted from 27th December 1813 to 23rd January 1814, in London, the tempera- 154 THE EARTHS ATMOSPHERE. ture varying during this period from 21 to 34 Fahr., that difference of temperature between the air and the water could not explain such a phenomenon. The fact is, that electricity plays a great part in the production and duration of fogs. An English observer, Thomas Eonayne, first discovered (in 1761) that fogs are highly electrical, quite as much so as clouds. His observations were published in the Philosophical Trans- actions, but attracted no attention till they were re- peated in 1774 by Henley. In more recent times, much attention has been given to the subject by Peltier, a Belgian observer. 1 The Earth being always electro-negative, the fogs are sometimes electro-positive, and sometimes electro- negative. In the latter case, being repelled by the soil, they do not wet the Earths surface. But there exists a rare kind of electro-positive fog which does not wet the ground either. Such was, for instance, the celebrated dry fog of 1783, which made its appearance at about the same time in many distant places, spread- ing from North Africa to Sweden. It exhaled a disagreeable odour, was remarkably dry (not affecting the hygrometer at all), and was decidedly luminous at night ; sufficiently so to enable a person to see objects at a distance of 600 feet ; and it lasted about a month. Fogs are often so electrical that they diffuse much light at night. 2 A remarkable instance of this was 1 Peltier, Memoire sur les diverses espece de JBrouillard, Bruxelles, 1842. 2 Phipson, Phosphorescence, etc., London, 1862 ; and Familiar ELECTRICITY. 155 noticed by Professor Wartmann, of Geneva (18th to 26th November 1859). The moon, being new, was invisible, but a vast fog, not damp enough to wet the Earth, but so opaque as to render invisible the borders of the river Leman and the Mont Saleze, lay over Geneva and its environs. It diffused so much light, that a person walking from Annemassa, in Savoy, on the 22nd November, saw his way as clearly as if it had been a moonlight night. Auguste de la Rive, the well-known electrician, made a similar observation about the same time. In 1863, Dr. Meissner, of Gottingen, 1 showed that moist air submitted to the action of electricity in closed tubes produced a mist, which did not disperse on being passed through water, but appeared again on the surface of the water, and lasted about half an hour, after which it gradually disappeared, depositing dew on the sides of the glass vessel. It is probable that if a few high towers, surmounted by very long metallic rods communicating properly with the Earth, were erected around our large cities, the latter would be rarely or ever troubled by thunderstorms. Such an arrangement would likewise prove very beneficial in the wine districts of France, in such places, for instance, as the little town of Tonnerre (ominous name !), where thunderstorm^, with hail, cause so much destruction to crops and property. It has been Letters, London, 1876. Peltier, Memoirs of the Acad. of Sc., Brux- elles, 1842. 1 Meissner, Untersuch. iiber den Sauerstojf, Hanover, 1863. 156 THE EARTH'S ATMOSPHERE. recorded that the late Professor Charles, a well-known French scientist and aeronaut, more than once succeeded in arresting the progress of a thunderstorm, which was approaching Paris, by sending up an immense kite with a metallic string. When I resided in Paris, before the Franco-German war, the wooden stand to which this kite was attached was still preserved at the Conservatoire des Arts et Metiers \ the wood appeared to have been thoroughly calcined by the numerous electric discharges that had fallen upon it from the atmosphere. Dr. Lining, of Charlestown, U.S., and De Romas, of Nerac, in France, seem to have entertained no doubt on this subject ; and once Frangois Arago said that he believed the problem of transforming thunder-clouds into ordinary clouds had been solved. Ib is admitted that, by sub- tracting their electricity, thunder-clouds can be pre- vented from forming hail; and if this be really the case, it would be most important to establish in certain districts a catching agency of captive balloons, kites, or towers with metallic rods, communicating with a water- course, or with the moist soil ; for not a year passes but hail does great damage at such places as Rieux, Comminge, Lombez, Tonnerre, etc. Some time ago I saw an official report that showed damage to crops amounting to one million pounds English money, after a single thunderstorm in France. The kite which M. De Romas flew at Nerac, the string of which was surrounded by fine copper wire, effectually subtracted electricity from the storm-clouds ; and whilst these experiments lasted, no lightning was ELECTRICITY. 157 seen, nor thunder heard. Yet this kite only rose about 160 yards into the atmosphere ; and in presence of com- paratively small thunder-clouds, he drew from the string flashes of lightning from 7 to 10 feet in length. In less than an hour he got as many as thirty of such flashes. CHAPTER XXIV. Atmospheric Tides Magnetic Storms Sabine's Observations- Absorption of the Moon's Atmosphere. THE attraction of the Sun and Moon upon the waters of the Earth, giving rise to the phenomenon of tides, it is evident that atmospheric tides must be produced in the same manner, and affect the weather to some extent. But no exact laws in this respect have yet been established, and it is impossible to refer change of weather, in any given locality, to the influence of the Sun and Moon upon the atmosphere. Popular notions on the effects of a " change of moon " upon the weather are not borne out by scientific observations. 1 In reading the works of Maury, a modern scientific observer cannot fail to be struck with the immense amount of work which still requires to be done with regard to the origin or cause, and even as to the directions of the various currents of the ocean and the atmosphere. His writings bristle with hypotheses 1 See on this subject P. Garrigou-Lagrauge, "Relations entre les mouvements barometriques et les mouvements en declinaison du Soleil et de la Lune '' (in the Comptes-rendus of the Paris Academy of Sciences, llth February 1895, p, 342). See also a note by another author in the Comptes-rendus for the 10th February 1896. TIDES MA GNETISM ABSORPTION. 1 59 which observation has not yet confirmed, though he has given us a considerable amount of useful experience. Nevertheless, his notion of the cloud-ring of the equatorial regions, which he likens to the ring of Saturn, his belief in a current of air that reaches us from South America, carrying red dust, in which Ehrenberg found the same kinds of infusoria in whatever part of the globe this red dust was collected, the statement that the magnetic condition of the Earth may produce a retardation in the progress of winds, and many other haphazard statements, where imagination plays a much larger part than direct experiment or observation, must not be allowed to mis- lead us in the calm investigation of Nature's mysteries. Humboldt is one of the few observers who have never allowed hypothesis to take too large a place in his writings ; and, at the present day, the patient labours of the scientific expeditions, like that of the Challenger, or even the more modest work of the Prince of Monaco and the late Georges Pouchet, will, in after years, enable us to reap far finer practical results than can ever be expected of mere theory. We have yet said little of the magnetic condition of the atmosphere, the most difficult, complicated, and least known of all its phenomena. The wonderful discovery made by Faraday of the paramagnetic property of oxygen gas, ''showing that it takes polarity by the action of a magnet, just as iron does, can have little or nothing to do with the beautiful phenomenon of the Aurora borealis and australis, which must have existed long before free oxygen gas 160 THE EARTHS ATMOSPHERE. existed in the Earth's atmosphere, that is to say, long before the advent of plant life. During the Aurora the magnetic needle is affected very powerfully, just as an ordinary electric current affects it. The so-called magnetic, storms, which occasion- ally interfere with the working of the electric telegraphs in all parts of the world, mostly come on without any previous warning, as we observe to be the case with earthquakes. It is not yet certain whether these magnetic storms are connected solely with the gaseous envelope of our planet, with the Earth's solid crust, or with some region underneath this crust. The observations of Sabine l have shown conclusively that the periodic variations of the magnetic activity of the Earth cannot be based on periodic changes of temperature in those parts of the atmosphere which are accessible to us. Nor do the epochs of these periods coincide with the maxima and minima of the tempera- ture of the atmosphere. Nevertheless, the influence of the Sun's position upon the manifestation of the magnetic force of the Earth was known at a very early period. Kepler discovered the horary variation of the magnetic needle, and believed that all the axes of the planets were magnetically directed towards one portion of the Universe; he thought that the Sun may be a magnetic body, and, on that account, the force which impels the planets may be centred in the Sun. Horrebow in 1730, who did not confound gravitation and magnetic attraction, thought that light was the 1 Phil. Trans., 1850. TIDES MA ONE TISM ABSORPTION. 1 6 1 effect of a perpetual aurora produced in the Sun's atmosphere. In both hemispheres, the epoch at which the intensity of the terrestrial magnetic force (whether in the atmos- phere or elsewhere) is greatest, is identical with the period at which the Earth is nearest to the Sun, and consequently when its velocity of translation is greatest. Whether magnetism increases as we rise in the atmosphere is a disputed question of minor importance, since the great currents of the air keep its temperature and electric condition in a constant state of change, though its chemical composition remains apparently constant. When the electric current, to which the Earth's magnetism may possibly be due, is caused to flow through very rarefied air, it gives rise, as everyone knows, to appearances similar to those of the Aurora. Humboldt observes that " it would be inconceivable if, amid the harmonious co-operation of all the forces of Nature, the paramagnetic property of oxygen gas and its modifications by an increase of temperature should not participate in the production and manifestation of magnetic phenomena." But all this is mere suggestion ; and it is far more probable that magnetic phenomena occurred, as I have already intimated, before any free oxygen existed in the atmosphere. It is certainly a singular fact that oxygen, hitherto, is the only gas which has been found to be paramagnetic. The atmosphere is not only an essential medium for the life of man, but for the life of the entire globe. No manifestation of life on the Earth would be apparent 1 62 THE EARTH'S ATMOSPHERE. if there were no atmosphere ; and should it be finally proved that our satellite, the Moon, is quite devoid of an atmosphere, it must be considered as a dead globe, like the meteorites, which in all probability circulate also round the Earth. But, strange to say, traces of organic matter, which may or may not have been derived from organized beings, have been discovered in meteorites. Some believe that the Moon once had an atmosphere like that of the Earth, but that it has been absorbed. What would happen if the Earth's atmosphere were to be absorbed is too dreadful to contemplate. The whole life of the globe depends upon it ; and we could conceive nothing more desolate, cold, soundless, dark y and dead than the Earth deprived of its essential envelope. APPENDIX A. I. Account of an Experiment made with Convolvulus arvensis vegetating in an Atmosphere devoid of Oxygen. IN addition to the experimental notes I have already published to demonstrate the truth of my new theory as to the origin of atmospheric oxygen, I give here the details of an experiment made with Convolvulus arvensis, a plant which I have often used for this purpose, vegetating in an atmosphere quite devoid of free oxygen, whilst two other plants of the same species were growing alongside of the apparatus as "witnesses," in ordinary atmospheric air. This is one of the experiments which first showed me that the plants of our present epoch are truly anaerobic, like those of former geological periods, and that free oxygen in the air is not essential for their existence. This experiment with Convolvulus arvensis, vegetating in what may be termed a "primitive atmosphere," is typical of what occurs with all the phanerogamic plants previously mentioned, and with the green unicellular algae such as Protococcus palustris and the minute Microcystis or Chalmi- domonas, etc., which develop in spring water exposed for some weeks to the light. The nitrogen was obtained from pure sulphate of ammonia, 1 64 APPENDIX A. or by the action of potash and pyrogallol on atmospheric air. It will be seen by what follows that the same volume of nitrogen may be used over and over again, as it under- goes no alteration in volume or properties, except such as are due to oscillations of temperature and pressure. The apparatus consists of a graduated tube, wide enough to admit the plant easily, standing over water containing minute quantities of all the substances known (or supposed) to be necessary to vegetation, and kept supplied with carbonic acid. Alongside the graduated tube stands a smaller tube full of water. Into this smaller tube carbonic acid is introduced, at first once a day ; it displaces the water ; but in the course of twenty-four hours the water has absorbed this gas, and the tube is again full of water. Carbonic acid is again passed into it next day, and the water displaced, now saturated with carbonic acid, thus finds its way to the roots of the plant. In this manner the water of the basin in which stand the two tubes is kept supplied with an appropriate quantity of carbonic acid. The whole apparatus is exposed to a constant northern light, such as is used by artists, which I have found preferable to a southern aspect, or to the direct rays of the sun. The temperature of the laboratory whilst this experiment was carried out varied from about 60 to 90 Fahr. One-half of the water in the little basin is covered with a piece of plank, to procure darkness for the roots, and a certain amount of carbonic acid is let into the wide graduated tube from time to time. APPENDIX A. 165 In this " primitive atmosphere " of nitrogen, containing some carbonic acid, and vapour of water, vegetation is found to be tolerably prosperous, in spite of the confined condition of the air: the carbonic acid is absorbed and replaced by free oxygen, so that after a certain lapse of time the gas in the graduated tube approaches the composition of ordinary atmospheric air, and can even be made richer in oxygen than the latter. First 75 cubic centimetres of pure nitrogen (reduced to C. and 30 inches barometer) are introduced, and the little plant being put in, makes the whole 102 centimetres. Then a small amount of carbonic acid is let in, and the volume of gas oscillates during the experiment from 102 to 130 c.c., according to the temperature and barometric pressure at the time of observation. The little plant of Convolvulus arvensis was introduced on the 25th July 1893, its height being then 30 divisions of the graduated tube. On the 26th July it had grown to 37 divisions. 8*th 44 29th 48 30th ,, 51 when it began to curve. On the 31st July it had formed a new leaf and was curving ; it now occupied 52 divisions of the tube. On the 1st August it had curved considerably, as all plants of the genus Convolvulus do, and measured only 50 divisions in height ; but on the 2nd August it had shot up again to 64 divisions. It appeared very healthy. On the 3rd August it attained to 68 divisions. 166 APPENDIX A. On the 5tli August there were new leaves formed, and the plant measured now 70 divisions in height. During the 6th, 7th, 8th and 9th of August, the plant was healthy and two more new leaves had formed. The water being well supplied with carbonic acid, and a little of this gas again introduced into the graduated tube, I left the experiment (in order to make a journey) until the 18th September. On the 18th September my Convolvulus had grown to 90 divisions ; and by the 30th of that month to 94 ; nearly to the top of the tube. On the 2nd October, it began to turn yellow, as did also the two plants growing in water outside the apparatus as " witnesses " ; they all three put on their autumnal tints at the same time, and had ceased to vegetate by 30th October. The gas in the graduated tube (reduced to C. and 30 inches barometer) then measured 95 cubic centimetres. It was analysed on the 30th October, and gave exactly the following result: Nitrogen, . '"' * 75 cubic centimetres. Carbonic acid, . none Oxygen, . 20 Total, V . 95 Thus in the course of three months and seven days, or ninety-eight days, the little plant had grown from 30 to 94 divisions, not counting the curve, natural to the Convolvulus, and had converted all the carbonic acid into oxygen, leaving the nitrogen exactly as it was at the commencement of the experiment. APPENDIX A. 167 At the end of these fourteen weeks the atmosphere of the graduated tube was richer in oxygen than ordinary atmos- pheric air. II. ADDITIONAL NOTES. 1. BUMBLING THUNDER. There is a curious passage in Galvani's paper, De Viribus Electricitatis, etc., 1791 (Bologna), on the use of a frog's leg, properly prepared, as an electrometer, or electroscope. Dr. Galvani wished to try whether the electricity of the atmosphere, or the clouds, would produce the same effect on the prepared limbs of a frog as is produced by the artificial electricity of ordinary machines. He had already noticed, independently of the convulsions caused by the direct contact of the limbs with the conductor of an electric machine, that whenever a spark was taken from a large conductor situated at some distance from the prepared limbs, the legs moved with a kind of spasmodic contraction, sometimes strong enough to cause them to jump a little. In order to ascertain whether atmospheric electricity would act in the same manner, he placed a conductor at the top of his house in Bologna, and put this conductor in connection with the prepared frog placed upon a table in the open air, or enclosed under a glass bell, and he soon observed that lightning produced the same effect as the sparks of an electric machine at,, a little distance. The same contractions of the limbs occurred, and they were stronger, or weaker, according to the distance and quantity of the lightning. Thus far the effects might, naturally, have been expected ; 168 APPENDIX A. but a remarkable circumstance was observed which seems to explain another phenomenon of nature : it was found that instead of one contraction at every clap of thunder, the frog's limbs were affected with a sort of tremor, or succession of convulsions, which seemed to be nearly equal in number to the repetition of the thunder, namely, that succession of explosions which cause the rumbling noise of thunder. This observation, he imagined, proves that the rumbling noise is not the repeated echoes of a single explosion, as had been generally admitted, but that it is produced by a quick succession of several ex- plosions. This is, no doubt, very true; but the effect of echo may likewise play its part, as Galvani himself would have admitted could he ever have heard a pistol discharged on a Ehine boat passing the famous Lurleyberg on a fine summer day. 2. BOOMING NOISES IN THE AIR. I have, on more than one occasion, whilst sitting of an afternoon on the sand- hills of Ostend on hot, calm days of summer, heard booming sounds in the air, just like the reports of distant cannon. This subject gave rise, many years ago, to some correspond- ence in certain geological journals, and it was sought to prove that what I had heard so distinctly, was really due to the sound of cannon, during artillery practice carried by the water from the English or French coasts. However, I have since met with accounts of similar sounds being heard in South America, and in India, at places where no sounds of cannon could by any possibility be heard; and these singular booming sounds, which only occur in the calmest weather, when there are no clouds, APPENDIX A. 169 and no wind, still require explanation. At the time I first heard them, I took every means of assuring myself that they could not be due to ship's guns at a great distance, or to artillery practice hundreds of miles distant. More- over, I never heard them more than twice or three times in an afternoon. Still, from the nature of the sound this, in the present state of science, would be the only explana- tion possible, had I not met with accounts by travellers in South America, and India, of precisely similar effects having been noticed by others under circumstances that precluded the idea of their being reports of guns at a great distance. 3. LATEST OBSERVATIONS ON ATMOSPHERIC ELECTRICITY. A history of these observations is given in my work Familiar Letters on Some Mysteries of Nature (1877), and in my previous work Phosphorescence (1862). Since the dates at which they were published, many thousands of observations have been made, confirming all that is there stated, but adding no new discoveries of importance. The recent work of the Austrian philosophers, Elster and Geitel, on the higher Sonnblick (about 10,000 feet above sea-level), add little or nothing to what was known in the time of Frangois Arago (Notice sur le tonnerre, 1838). They have found, at this height, that in storm-clouds there is a change in the sign of the electricity after every flash of lightning, just as we observe in the plains or valley s % They also find, that St. Elmo's fire is a constant accompaniment of storms, and is sometimes positive and sometimes negative not more frequently one than the other. Negative St. Elmo's fire follows bluish lightning, and positive St. Elmo's fire follows 1 70 APPENDIX A. reddish lightning. This fact was frequently confirmed ; whence these observers conclude that the direction of the electric current which traverses the atmosphere appears to have an influence on the colour of the lightning. To this I may add, that whenever I have witnessed a stroke of lightning, it has always appeared as a red globe, about the size of a cannon-ball, which, taken in connection with the fact that the Earth is always negative, is worthy of note. Nevertheless, it is known that the electric spark is of various colours when passing through different gases, being very white in carbonic acid, reddish or purple in hydrogen or ammonia, etc. Hitherto, without the aid of direct experiment, I have thought that blue lightning occurred in dry air, and red lightning in wet air. In 1889, M'Lean and Goto, in Glasgow, showed that an enclosed mass of air is electrified negatively by the burning of a paraffin lamp, coal-gas, sulphur, magnesium, and many other substances. But the burning of charcoal electrified a room positively. When ventilation is active no electriza- tion of the air of a room is perceptible by these means, 4. SMOKE IN THE AIR OF TOWNS. Dr. Cohen of Leeds has calculated that in that town alone, about one ton of smoke is launched into the atmosphere every hour (the exact figures found were twenty tons a day). A large amount of this falls as soot, darkening the air, and fogs, and blackening the skins of men and the leaves of plants. He finds in this soot 14 to 15 per cent, of what he calls a "nasty, sticky oil," which has an unpleasant odour, and causes the soot to adhere so firmly to the leaves of plants, that it requires an immense amount of rain to wash it off. The carbon and coal-oil of APPENDIX A. 171 soot, nevertheless, act as antiseptics, and are not so harmful as many people suppose. 5. THE DUST THEORY OP KAIN. Of late years a new theory has been put forth regarding the formation of mist, fog, cloud, and rain. It is asserted that without dust in the air that is, microscopic fragments of sand, sea-salt, organic matter, etc. there would be 110 mist or rain. The starting- point, it is said, of each drop of water is a minute nucleus of dust- an infinitesimally minute fragment of salt or sand ; " a microscopic speck of sand, around which the vapour of water condenses,' 7 as a man puts on an overcoat. Without this dust, which is always present in the lower atmosphere, the vapour of water, on a cooling of the air, would be deposited on the ground in sheets of dew that would soak the buildings, and gardens, etc., but there would be no mist, fog, or rain. This theory is based upon a simple experiment, which con- sists in exhausting some air from a large glass globe full of moist air. If that air be perfectly free from dust, no mist is formed when the air is thus cooled ; but if a little dust is blown in, mist forms as soon as the piston is worked again. It is probable, however, that electricity may be capable of forming mist or fog in perfectly pure air saturated with moisture. When ozone is passed through water into air, confined in a glass vessel, a mist is formed in the latter, whether there be any dust or not. 6. ODOUR OF THE ATMOSPHERE. In addition to what I have already said on the odour of the air, experienced in travelling from one country to another, on the odour of the 172 APPENDIX A. air after a summer shower, on the fact that ancient fossils of the tertiary period have revealed to me that sea-air had the same odour as now in times excessively remote, I may record here that, according to Dr. Varigny, the atmosphere itself, which is generally considered to be inodorous, really has an odour sui generis. In his opinion the air that usually surrounds us is full of all kinds of scents and odours, but we are so accustomed to them that they attract no attention. But after spending some time in an atmosphere where the most ordinary odours cannot gain access, and then returning to our ordinary surroundings, the case is altered and a very powerful odour is perceived. This fact has been noticed by various observers who have sojourned for a considerable interval in deep caves. The air of these caves is nearly odourless, and when, after a few hours spent in this "scentless air," the visitor emerges into the open air of the country, he perceives that the atmosphere has a peculiar and very intense odour, by which delicate people in these particular circumstances have been, more or less, strongly affected. But, after all, it is not the atmosphere itself which affects the olfactory organs in these circumstances, but the numerous extraneous substances that are constantly present in its lower strata. So that Dr. Varigny's supposition that the atmos- phere has an odour sui generis is by no means proved. 7. FREE OXYGEN IN BIVER WATER. The amount of free oxygen found in the air dissolved in river waters varies according to the purity of the water. In the absence of impurities, there is far more oxygen than when impurities are present ; and we can determine the degree of purity of a APPENDIX A. 173 river water by simply ascertaining the amount of. free oxygen which it contains. For instance, the Thames at some distance above London yields 7*4 parts of free oxygen, at Hammersmith 4*7 parts, at Somerset House 1'5, and at Woolwich 0'25. These figures speak for themselves. Most river waters yield from 4 to 8 cubic centimetres of free oxygen gas per litre (or quart) of water, according to circumstances. The more oxygen gas thus found, the purer is the water, and better for drinking. The pure water of the Khone, far from towns, will give 8*4 cubic centimetres of oxygen gas to the litre of water, whilst the water of the river Seine at Paris only yields 3*9 cubic centimetres. 8. IMPORTANCE OF THE FREE OXYGEN KATIO IN THE AIR, In a recent pamphlet on Air and Life, Dr. Yarigny states that living beings are adapted, at the present period of the life of the globe, to exist in an atmosphere containing J of oxygen, and f of nitrogen. Experience shows that if the ratio of oxygen be decreased even by th part, life can no longer be main- tained. Paul Bert has shown that a change in the contrary direction is, also, most deleterious. If the oxygen acquires a certain tension in the atmosphere or, what amounts to the same thing, if it be present in a certain ratio above the normal it becomes an agent of death, both for plants and animals. This he demonstrated by causing plants or animals to live in a normal atmosphere, but under a high degree of pressure ; or by placing them in an artificial atmosphere containing a large excess of oxygen. In both cases death was the result. 174 APPENDIX A. 9. OZONE IN THE ATMOSPHERE. The absolute quantity of ozone, or condensed oxygen (3 volumes condensed into 1), rarely exceeds 1 part in 10,000 parts of air. Its presence is a fair guarantee of the purity of the air, but an excess of ozone is deleterious to persons suffer- ing from bronchitis. Ozone has been liquefied at 100 C. below zero, with a pressure of 127 atmospheres. It then forms a liquid of a dark indigo-blue colour. Gaseous ozone, viewed endways through a tube a yard long, also shows a blue colour. 10. WATER VAPOUR IN THE ATMOSPHERE. The average quantity of water vapour in the air near sea level, in most countries, is from 60 to 75 per cent, of that required for complete saturation. The phenomenon of the rainbow proves that rain-drops are perfectly spherical in form ; for this phenomenon can only arise from the regular dispersion of white light by transparent globules of a perfectly spherical shape. In- stantaneous photographs also show them as perfectly globular in form. Observations made, of recent years, from the earth, on mountains, and in balloon ascents, have shown that the tower of a cumulus cloud often exceeds 10,000 or 15,000 feet, and in great storms may be 25,000 to 40,000 feet from base to summit. 11. LATEST CONSIDERATIONS ON "ARGON." Lord Kay- leigh has said, " We are not able to state with certainty whether argon is a mixture, or, if it be, of how many elements it consists. The spectroscopic evidence points in APPENDIX A. 175 favour of at least two components, but of itself is not conclusive." And, again, " the density of argon is approxi- mately 20." This causes me to believe that argon may ultimately be found to be a carbide of nitrogen, CN, having half the quantity of carbon contained in cyanogen. Such a com- pound would have a density of 20, and may yet be artificially prepared in the laboratory. This, in spite of the fact that considerations, derived from the specific heat of this new gas of the atmosphere, show that it must be considered an element, according to our present experience. "Helium" is another gaseous body, which is still under investigation by Dr. Ramsay, and this chemist has recently (1898) found still another gas, which he calls " Crypt on" (or "hidden"), and has obtained as a residue from the evaporation of liquid air. He believes it is present in the atmosphere to the extent of-1 part in 20,000 parts. The new gas "Argon" is found to form about 1 per cent. of our Earth's atmosphere, and, like nitrogen, has little or no affinities for other substances. It was first seen by Cavendish in the last century, and by Van Marum, a Dutch chemist, when they subjected atmospheric air to the action of the electric spark, with the view of obtaining nitric acid. There always remained a residue in these experiments, and this residue consisted largely of " argon," together with the other gases which had escaped the action of the electric sparks. 1 ^ 12. HIGH READINGS OF THE BAROMETER DUE TO THE 1 A letter published in the Chemical News of 17th June 1898 shows that Rayleigh and Ramsay have really isolated no new elements, but only mixtures of gases. 176 APPENDIX A. MOON'S ACTION. I have sometimes been surprised at the remarkably high, reading of the barometer extending over a month or more in England, and Northern Europe gene- rally, and independent of the direction of the wind or state of the weather. Such was the case, for instance, in January and part of February 1896. This phenomenon has been carefully observed by Mr. Dechevrens, of Jersey (director of the St. Louis Observatory in that island), and he attributes it decidedly to cosmic influence, that is, to the position of the Sun and Moon with regard to the Earth, and especially to the distance of the Moon : the greater the distance of the Moon the higher the glass stands, and the nearer the Moon is to the Earth, the lower the barometer. The Moon acts upon the atmosphere as it does upon the ocean to produce the tides ; and the nearer our satellite happens to be to the Earth the greater is its attraction, and the lower the barometer. By studying the fluctuations of the barometer since 1750 to the present time, Mr. Dechevrens has discovered that this high reading has a period of 19 years, and in making these researches he has, moreover, discovered a general increase of atmospheric pressure having 63 years between the maximum and minimum points, or a cycle of 126 years. 13. HYDROGEN GAS IN THE HIGHER EEGIONS OF THE AIR. It will be remembered that one of our greatest chemists, the late Professor T. Graham, who was for some time Master of the Mint, discovered a small quantity of hydrogen gas in meteorites (aerolites), composed chiefly of iron and nickel, more especially on the Leanarto meteorite, which APPENDIX A. 177 contains 90 parts of iron and 8 parts of nickel, with a little cobalt. When heated in a porcelain tube a quantity of hydrogen gas, amounting to about double the volume of the meteorite, was obtained. Hence he concluded that meteors traverse a region of the heavens in which hydrogen gas is contained; and he calls attention to the fact that the rays of hydrogen have been found in the spectra of certain fixed stars, and in the sun. The conclusion is not warranted, as this remarkable aerolite was, like all others, at an excessively high tempera- ture on passing through the air, and as our atmosphere, at least in the lower regions, is abundantly supplied with vapour of water, which would instantly be decomposed on the aerolite entering these lower regions, the conclusion is not necessary. It may be, also, that the hydrogen found in his experiment was simply due to the absorption of water into the pores of the -meteorite after it had fallen, which water would be decomposed when the meteorite was heated in the porcelain tube, and yield hydrogen gas. 14. ELECTRIC STATE OF THE AIR DURING CHOLERA EPIDEMICS. We must not pass over the very interesting results obtained by Professor Denza at the Observatory of Moncalieri in Italy, during an outbreak of cholera, which was very severe at Turin and other towns of Piedmont in 1867. These observations on atmospheric electricity by Denza were commenced regularly in December 1866, and were the first regular researches of this kind carried on in Northern Italy since Beccaria made the first experiments on the electricity of the air in fine weather about the M 178 APPENDIX A. year 1775, in the days of Benjamin Franklin and De Saussure. In these researches the tension of the atmospheric electricity was determined by Denza with the bifilar electro- meter of the late distinguished Professor Palmieri, of the Royal University of Naples. During the months of August and September 1867, when the outbreak of cholera was at its height in Turin, the electric tension of the air fell to almost nothing, except on two days when there occurred storms (temporali). 15. LIQUID AIR. The liquefaction of gases by the appli- cation of cold and pressure combined has occupied many experimentalists for the last century, or more. It has now culminated in the liquefaction of atmospheric air by Pro- fessor Dewar of the Royal Institution. The curious chemical properties of this new fluid have been alluded to already, but its physical property as a motor power is no less wonderful. Liquid air is simply the air we breathe compressed in a series of cylinders, each successive cylinder pressing the air into a smaller and smaller compass, the air after each pressure passing through cooling tanks until, finally, when squeezed into about g^th of its original volume and cooled to about 312 below the freezing-point of water, it changes from a gaseous state into a liquid. When this liquid is again exposed to the ordinary tempera- ture of our rooms or streets, it expands to its original volume with such power and rapidity as to exert a pressure of more than 12,000 Ibs. to the square inch, which is a truly explosive force exceeding that of dynamite itself. APPENDIX A. 179 One gallon of liquid air weighs 7 Ibs., and we are assured that, in round figures, about 1 Ib. of coal is required to make 1 Ib. of liquid air. Hence it must be a very economical source of power. It has been asserted that one cubic foot of liquid air will develop, on gradual expansion, 5J horse-power per hour, or 1 horse-power for 5 J hours ; and it is believed by some practical men, that this enormous power will soon supersede steam, electricity, and all other sources of power, and that it can be controlled and managed as easily as any of them. To make liquid air is one thing, but to devise machinery for its utilization as a motor power is another ; but both these results, I am told, have been recently carried out by an Anglo-American firm, which has already placed on our streets motor cars driven by the gradual expansion of liquid air confined in a powerful cylinder; and there seems some probability of liquid air being produced cheaply in large quantities and applied economically as a motor power in various branches of industry. 16. FIELD LIGHTNING. I find that the singular pheno- menon described in my Mysteries of Nature as Field light- ning, and alluded to in Chapter IX. of the present work, has been witnessed in Mongolia as well as in the Jura Mountains. Mr. A. B. Freeman Mitford, C.B., in a work on Peking, issued quite recently, describes a storm he experienced in Mongolia on 7th May 1867. He says : " About two njiles from Llama Miao, where the storm had lashed itself to its greatest fury, we came to a small plateau surrounded by low hills. Here we witnessed a phenomenon, new to me, and which I certainly never wish to see again. The thunder, which i8o APPENDIX A. seemed to circle round the hills, roared savagely and cracked with deepening peals, while the lightning ran along the ground, criss-crossing in every direction, until the little plain was covered with a perfect network of Hue liquid flames, from the meshes of which escape seemed impossible" APPENDIX B. Outlines of a New Atomic Theory. By Dr. T. L. PHIPSON, F.C.S., etc. ; read at the British Association for the Advancement of Science, Sept. 1886. IN what follows, the term phlogiston is used in a somewhat different sense to that in which it was employed by the older chemists. Some other term might have been equally acceptable, but this one already belongs to chemistry, and therefore we have a predilection for it. On a general survey of organic and inorganic nature, our attention is arrested by a number of facts, which, though they have hitherto defied explanation, the present considera- tions appear to account for, so far as we can account for anything by connecting facts with theory. Nevertheless, the theory we now put forth does not necessitate any great change in the nomenclature or teaching of chemistry ; if it represent truth, it should be given to the world, though for many years we have hesitated to publisji it. In chemistry we have an immense list of substances, all of which present themselves as colourless fluids, or white powders, though differing as widely in their properties as pure water and prussic acid on the one hand, or arsenious 182 APPENDIX B. acid and sugar on the other. Wine-glasses filled with water, alcohol, ether, sulphuric acid, solution of potash, etc., present no difference to a child or a savage ; neither would their contents be considered anything else than water if they contained a solution of some nitrate, chlorate, sulphate, sugar, strychnine, veratrine, ammonia, cyanide of mercury, and so forth. In like manner, all the metals present what is termed the "metallic aspect"; they all show a great similarity of physical and chemical properties, so that tin, silver, cadmium, zinc, antimony, sodium, mag- nesium, aluminium, lead, etc., would readily be mistaken one for the other by a child or inexperienced person. Again, the alkaloids, sugars, glucosides, essences, etc., all present a great similarity in their physical and chemical properties, a likeness which extends to their therapeutic qualities also. Another fact, which has often struck chemical philoso- phers, but has hitherto baffled all attempts at explanation, is that of all the numerous elements, or simple bodies, which compose our globe, four alone are found sufficient to build up the whole of organic nature, and to form the thousands upon thousands of substances known as organic compounds. One more fact, which is amply demonstrated by the numerous analyses given in one of our works, is that meteors or aerolites coming from distant regions of space bring no unknown matter to our globe ; they are composed of the same materials as our earth. It will be seen by what follows that the same materials may possess different properties, according to the circumstances in which they are placed. APPENDIX B, 183 A phenomenon, readily explained by our new atomic theory, though it has hitherto not been accounted for satisfactorily by any hypothesis, is that observed when two substances of heterogeneous natures, such as two metals, are brought into contact, an electric current, or electric, calorific, or magnetic manifestations, immediately occur. The old notion that matter is composed of " atoms and spaces" is doubtless correct, and it can be argued success- fully that atoms are extremely minute spheres. When one substance is divided by another (as when an apple is cut by a knife), the latter passes between the atoms, for matter is impenetrable, that is to say, the same space cannot be occupied at the same time by two groups of matter or by two substances ; one must make room for the other, and the space betiveen the atoms is what we designate as phlogiston. The whole question of the atomic constitution of matter is contained in the theory of equal gaseous volumes, or better, of the combining volumes of matter in the state of gas. When we consider this subject, we are met at once by a dilemma. Physical experiment having shown that between certain limits of temperature equal gaseous volumes dilate or contract equally for equal amounts of heat or pressure, it was argued that equal volumes of gases contain the same number of atoms of the same size and placed at the same distance apart. This, of course, implies that the atoms are of different weights (for instance, the atom of H weighing 1, that of N weighs 14, etc.). But it soon came to be seen that this could not be, because in equal volumes of certain compound gases we know that there cannot be an equal number of atoms. i84 APPENDIX B. The next supposition was that the atoms in equal gaseous volumes may be of different sizes. Thus the atom. of H would be 14 times smaller than the atom of N, etc. There is nothing to be said against this hypothesis, except that it does not explain anything ; it merely asserts that the atom of N is 14 times as heavy as the atom of H, because it contains 14 times more matter. This notion is, on many accounts, improbable, unphilosophical, and explains nothing. But another proposition, which we shall now put forward, does explain a number of phenomena that otherwise we find it impossible to account for. This proposition is that equal gaseous volumes contain a different number of atoms all of the same size and same weight. This implies that the atoms are all of the same nature, and proclaims the unity of matter. Whatever substance may be under consideration, its atoms are all of the same nature, and they are separated by space, which we call phlogiston, a term that implies movement, light, heat, electricity, etc. The greater the amount of phlogiston the greater the energy of the system of atoms termed element. Thus H is the most energetic system of atoms yet known ; it has the greatest amount of phlogiston; in other terms the motion of its atoms is the most extensive. The matter of all the elements is therefore identical ; the phlogiston alone varies, that is, the distance or space between the atoms (considered at rest), or their extent of motion. A chemical element is therefore a system of atoms, the nature or properties of which system depends on its phlogiston, and the amount of the latter is deduced directly from the balance from the weights which combine APPENDIX B. together. Thus in equal gaseous volumes of we admit that there exist, say, 10, 140, 350 atoms of the same size, same weight, and same nature ; and if we could volatilize without decomposing solid bodies such as sulphate of iron, for instance, so as to consider them under the same gaseous volume, we should find the same law hold good for them, and that an equal gaseous volume of ferrous sulphate, for example, would give, as compared with the substances above-named, 760 atoms of the same nature as those of H, N, or Cl. It will be seen by this that the properties of a substance depend not on different kinds of matter, but on the different amounts of phlogiston that separate the atoms and cause them to move in certain set systems. The atomic system called H is different from the atomic system called N, because the atoms of the latter system are separated by less space; the system possesses less phlogiston. We thus see that, as everything depends on gravitation, the systems of atoms (elements) known as iron, oxygen, sulphur, etc., on this globe, may possess very different properties on the planets Venus or Jupiter, for instance, on account of the different distances of these planets and our globe from the sun. Spectral analysis, like the fall of aerolites, proves that the same nature of atoms exists in far-off globes as with us ; but we see that the properties of a substance depend on its phlogiston, which in its turn depends on gravitation, so that although the matter is identical with that of our earth, the physical and chemical properties must be different from what they are upon this globe. We also see how the whole organic world is made up of 1 86 APPENDIX B. a few systems of atoms (elements) only; they are those which contain the most phlogiston, and consequently possess the most energy; they constitute the nearest approach to vitality. Again, when two heterogeneous systems of atoms are brought in contact, a vibration ensues such as astronomers have termed perturbation ; it is caused by a slight deviation of the movement a slight change in the phlogiston (which may be temporary or permanent), and is carried away along a "conductor," in the form of what is called an electric current, or otherwise. In allotropic bodies the original phlogiston is more or less permanently modified ; and could this allotropism be pushed far enough, the " transmutation " of the elements would undoubtedly ensue. It will be perceived that this theory explains a mass of facts, which are not even alluded to in the foregoing notes ; and though it leaves unaccounted for a certain number of physical phenomena, these will probably be explained in time without disturbing it. INDEX. ABSORBING power of the atmos- phere, 39. Aerolites, phenomena of, 135, 136. Air, compressed or rarefied, in medical treatment, 83, 84, 173. its disinfection, 85, 8fi. electrified by combustion of paraffin, etc., 170. history of discovery of the gases in, 4. gun, 82. hot and cold, 96. of inhabited districts, 89. at sea off coast of Flanders, 34. of sea coast, 90. liquid, 40, 178. phosphorescence of, 51. sudden vibration of, 53. not an oxide of nitrogen, 33. variations of quality at Palermo, 30, 80. variations during cholera, 30, 105, 177. Algse in first fall of snow, 61. unicellular, as producers of oxygen, 26. Alps, air of the, 104, 105. phosphorescence of snow on the, 52. Altitude attained by British troops, 119 (note). best in India for Europeans, 98. Altitude, total, 75. Ammonia, its quantity in country air, 71. a volcanic product and a secretion, 36. and nitric acid, 35, 36. Anaerobic beings, 13. cells, their transformation, 27. ferments, 15. Analyses of air, 30, 89. Andre, Ch., observations in a balloon, 49. Anglo-Indian statistics, 97. Animal life, dawn of, 26. Antirrhinum, author's experi- ments with, 20. Apophyllite, ammonia in, 37 (note). Arctic regions, air of, 104. Argon, the gas called, 8, 91, 174. Arsenic, its danger as used by mountaineers, 103. Atlantic, atmospheric perturba- tions of, 133. Atmosphere of Cape Horn, 86. an unexplained condition of, 55. definition, 38. its height above sea-level, 74, 76. old opinion on its extension, 139. the primitive, 19. in remote geological periods, 9. of our present epoclj, 32. 188 INDEX. Atmosphere, the science of the, 1. its temperature at great altitudes, 78. the term, 89. Atmospheric tides, 158. mucilage, 59. oxygen, 18. Atomic theory, a new, 25, 181. Aurora borealis, 51. effects on the magnet, 160. Auroral arch, 130. B BACTERIA, their place in nature, 28. of the Arctic regions, 86. collected on cotton-wool, 71. and micrococci, fossil, in the air, -62. Barometer, history of, 7. its fall, as we rise in the air, 76. high readings of, 175. rules for the observation of, 146. wind, chief cause of its movements, 110. and < thermometer, opposite indications, 107. Baudrimont, his opinion on the atmosphere, 14. Bayen, his experiment, 6. Beccaria, his knowledge of phos- phoric phenomena, 52. Bedrooms, the air of, 101. Berlin, Dr. A., researches on snow-blindness, 56. Bert, Paul, observations on effects of air pressure, 173. Berzelius, his views on the ancient atmosphere, 10. his proof that air is a mix- ture and not a compound, 33. Birds, migration of, 66. Blood, effects of mountain air on, 73, 74. Bloody-finger grass, 68. Booming noises in the air, 168. Boussiugault, curious observation, 63, 64, Breathing affected by mountain air, 73. Breweries, the air of, 102. Briquet a Air, the, 53, 82. Bran, account of his experiment on air, 5. CAMPI, his discovery of marsh gas, 100. Captive balloon experiments, 77, 78. Carbon fixed in the earth, 13. as carbonic acid in the atmosphere, 90. Carbonic acid could never have predominated, 26. quantity of, issued by a chalybeate spring, 12. amount of, in music halls, 90. in London fog, 99. quantity in the earth's atmosphere, 14. a volcanic product, 26. Cavendish, his experiment on air, 92. Characin, cause of odour of marshy lands, 42. Charles, Prof., attempt to arrest the progress of a thunderstorm, 156. Chemistrj 7 , dawn of scientific, 2. Cholera epidemics, air in, 30, 1*05, 177. Cirrus cloud, 122. Climate for invalids, 87, 99. Cloud, its formation, 77. height of, 79. checks radiation, 97. Clouds, their formation, nature and forms, 121. Cloud-arch, curious phenomenon of the, 128. , tjCA Coal flora, 26. v "\~ Cold air more dangerous than hot air, 96. Colladon, Daniel, his use of com- pressed air, 82. Colour of atmospheric air, 40, 117. INDEX. 189 Coloured circles (not halos), as indicators of weather, 124. Combustion, ancient views of, 3. Consumptive subjects, best air for, 99. Convolvulus, author's experi- ments with, 20, 163. Cosmic dust, 66. Cumulus cloud, 123. Currents, aerial, 106, 115. Curve of average temperature, 133. Cyclones, their discovery, and nature, 111. local, 114. D DALIBARD, his experiment on lightning, 48. Davaine arid Pasteur, their obser- vations, 142. Dawn of animal life, 26. De Foe, his suggestion of circular storms, 111. Denza, electric observations, 177. Dewar, liquefaction of air, 40, 178. - Digitaria sanguinalis, 68. t Disinfection of impure air, 85. of hospital wards, 101. Dissard, A. 0., effects of change of medium, 29. Diurnal oscillations of the atmos- phere, 108. Dove, his " Law of Storms," 115, 117. Dry fog, 154. Duchesne, his first glimpse of nitrogen, 3. Dumas, J. B., his calculations, 10-11. Dust, analysis of, 61. raised by postilions, 50. of snow, 126. theory of rain, 171. E ECK VON SULZBACH, CUHOUS experiment, 300 years before Lavoisier, 6. Egypt, culture of opium in, 105 (note). Electric dust, 50. light from hats of travellers, 50. spark, colour of, 170. state of the air during cholera, 177, 178. state, fluctuations of, in the atmosphere, 108. Electricity, atmospheric, 48, 169, 108, 177. currents of, obtained from the air, 49. produced by condensation of vapour, 125. Elements, the, of the Ancients, 5. Elster and Geitel, observations by, 169. Epidemics, 143, 177. Eremacausis of organic matter, 16. Esquimaux, ; their "snow eyes," 57. Expansion of air by heat, 108. Explosions in coal mines, cause and remedy, 101. of meteors, experiment by the author, 67. FALL of sulphur during a storm, 42. Falls of foreign bodies through the air, 59. Faraday, his experiments on gases, 40. discovery of magnetic pro- perty of oxygen, 159. Fermentation, the air of, 101. Ferments collected from the air, 71, 72. their place in nature, 28. Field lightning, 50, 179. Figures of sun and moon dis- torted, 117. Fitz-Roy, his observations, 77, 78. rules for the barometer, 146. " Weather Book," 115. Flora and Fauna of the earth, 9. Fog of Dec. 27, 1813, 153. 190 JNDEX. Fogs, carbonic acid in, 99. electric nature of, 51, 153. in London, 70. ^Forests, air of, 93. Fossil microbes, 62. Teredo, 44. Franklin, his celebrated experi- ment, 48. Frogs transported by waterspouts, 69. Fungi, the class of, 28. G GALILEO, his discovery of the weight of air, 6. Galvani, remarkable experiment by, 167. Gautier, A. (see Hydrogen). Glare, its nature discussed, 55. Goethe, his observations at Gir- genti, 129. Gossamer, 65. Grass, bundles of, transported through the air, 63. ' ' Green matter " of water exposed to sunlight, 142. Grotta del Cane, near Naples, 99. Gulf stream, 114, 131. H HAIL, the phenomena of, 127. damage by, in France, 156. Halos, solar and lunar, 62. Hsematosis, 73, 103. Hartz mountains, 118. "Health resorts," 87. Heat, the "soul of the universe," 106. Height of the atmosphere dis- cussed, 74, 76. to which man can live, 75. Hemeralopia, or night-blindness, 57. Hoar frost, nature of, 126. Hoefer, F., on the apparition of plants, 13. Holothuria, respiratory functions of, 15. Hooke, Dr., detection of oxygen in 1665, 3. Houzeau, his theory of thunder- storms, 125. his weather table, 147, 150. Humboldt, an argument by, 13. observations on the snow line, 120. Hydrogen gas in the higher regions of air, 176. (A. Gautier, by passing sea air over red hot copper oxide, pretends to have found 2 vols. of hydrogen in 10,000 vols. of air.) vegetation in, 21. I J ICE CRYSTALS, fall of, 62. Ignis fatuus, 100. Immediate weather, 145, 147. Insects transported by the air, 65. Iron particles discovered in the atmosphere, 61. Julienne, his air machine, 82, 83. Junod, Dr., his use of rarefied air, 83. K KEELER, Prof., on Saturn's ring, ^138. Kepler, his magnetic discoveries, 160. Koene, Prof. C. J., on changes in the atmosphere, 10. Krakatoa, eruption of the volcano, 66. LAMARCK, views of, 13. Langley, experiments on the Californian mountains, 39. Lavoisier, his first analysis of the air, 4. Levy, analyses made by, 34. Liebig, on the composition of the atmosphere, 10. INDEX. 191 Light from crystallization, 53. phosphoric, in the air, in snow, etc., 50, 53. Lightning conductors, discovery of, 50. drawn from the air, 156. flash, its cause, 52. on the ground, 50, 179. stroke on a captive balloon, 50. stroke on the earth, 135, 136. Liquefaction of atmospheric air, 40. Liquid air as a motor power, 178. Local cyclones, 114. London fog, substances present in, 70. Luminous fogs, 154, 155. - meteors, height at which they shine, 75. M E, experiment by, 50. Macagno, Prof., analysis of air at Palermo, 80. Magnetic conditions of the at- mosphere, 159, 161. Mairan, his prize essay on the barometer, 110. Maize killed by blight, 105. Marcet, Dr., experiment on re- spiration, 99. Marsh gas, 100. Martins, Ch. , respiration of plants and animals, 11. Maury, researches of, 131. - his hypotheses, 158. May, cold days of, 98. Mayow, his celebrated pamphlet on oxygen, 3. Meissner, Dr., experiment on electrified air, 155. Meteoric dust in the Arctic re- gions, 67. Meteors, aerolites and falling stars, 61. - history of, 136. - cause of their explosion, 67. Miasma and Virus, 141. Microbes, 86, 87, 141, 143. Mines, air of, 100. Mirage seen in England, 103. Moisture, quantity in the air, 79. Monocellular organisms, 143. Moon, its influence on the atmos- phere, 158. action on the barometer, 176. Mountain air, 73, 103. Movements of the atmosphere, 106. Mulder, on changes in the atmos- phere, 11. N NAPHTHA, vapour distinguished from marsh gas, 100. Nervous system, its increase with that of oxygen, 14. Night blindness in Franco-Prus- sian war, 57. Nimbus, or rain cloud, 123. Nitrification, its explanation, 36 .Nitrogen, first glimpses of, 3, 4. the primitive atmosphere of the earth, 25. the nature of, 35. supposed extraction from air, 13. Nostoc commune, 68. ODOUR of the atmosphere, 171. air in beech and pine forests, 44. air after a stroke of lightning, 41. air of foreign countries, 42. in the air of marshy lands, 43. of sea air, 44. after a summer shower, 45. of fossil Teredo^ 44. Odours before thunderstorms, 53. Opium culture in Egypt, 105 (note). 192 INDEX. Optical phenomena of the atmos- phere, 117. Organic matter of the atmosphere, 140. Origin of aerolites, 137. Oscillations of atmospheric pres- sure, 108. Overcasting, sudden, 121 (note). Oxygen, its discovery, 4. its absence from the primi- tive atmosphere of the globe, 10, 25. its appearance in the primi- tive atmosphere, 19, 25. (free) in river water, 172, 173. Ozone, its nature and effects, 45. liquid, 174. PARIS hospitals, disinfection of air in, 85. Pasteur, discovery of anaerobic ferments, 15. and Davaine, 142. Pelouze, his views on the atmos- phere, 14. Peltier, his observations on fogs, 154. Period that will never be de- termined, 28. Periodic plants, 68. Perpetual snow and ice, 120. Phipson, Wilson \V., his en- gineering works, 81. Phlogiston, new signification of, 181. Phosphorescence of the air, 51. rain drops, 118. work on, 52. Piazzi - Smyth, experiment at Teneriffe, 39. rain band of the spectroscope, 80. Planets, their effects on our atmosphere, 97. Plants, anaerobic, 18. first producers of oxygen, 12. experiments on the growth of, in various gases, 19, 163. Plants, microscopic hairs of, 62. Primitive atmosphere, the, 19. conditions of the globe, 25. Protococcus as a producer of oxy- gen, 13. respiratory functions of, 15. Pyrites in hailstones, 67. R RADIATION effects, 95, 97. Rain band of the spectroscope, 80. dust theory of, 171. fall, influence of forests on, 95. fall, its quantity, 151. frozen, 104, 126. "of sulphur,'* the so-called, 69. without clouds, 104 (note). Rapidity of motion of the air, 109. Rayleigh and Ramsay, discovery of " Argon," 92, 174. Refraction of light, its effects, 117. Refrigeration of the atmosphere, 77. Reiset, his analyses of air, 14. "Residues" left in primitive times, 9. Respiration in lower forms of life, 15. equilibrium of plants and animals, 11. Richman, Prof., death by light- ning, 48. Romas, De, experiments on at- mospheric electricity, 156. Ronayne, Thomas, his discovery of the electric nature of fogs, 154. Rotation of the vane, 107. Rumbling thunder, 167. SABINE, auroral arch, 130. results of his observations, 160. INDEX. 193 Salt in the atmosphere, 64. rain, 102. Saltpetre, its formation, 36. Saussure, Benedict de, experi- ments of, in 1767, 49. Theodore de, researches of, 23. Schiaparelli, opinion on comets, 138. Schlagintweit, the brothers, alti- tude attained by, 119. Schroeder and Dusch, observa- tions by, 141. Schultze, his experiments, 141. Schwann, experiment on air, 141. Science of the atmosphere, the, 1. Sea, the air of the, 102. Smoke of towns, 170. Snow-blindness, 56. Snow, formation of, 126. Snowfall in a dining-room, 127 (note). Snow line, the, 120. Social mites, mysterious appari- tion of, 66. Sound, conduction by air, 73. Spectral lines of oxygen, 39. Spectre of the Brocken, seen in London, 118. Spiders' webs in the air, 65. Stagnant waters, air over, 100. "Star jelly, "60. Star shower of Nov. 1866, 51, 61. Stars, shooting, 138. St. Elmo's fire, 118. positive and negative, 169. St. Hilaire, Geoffrey de, his views, 13. Stone, fragments of, which fell in Birmingham, 69. Stratus cloud, 123. Sulphate of soda in the lower atmosphere, 64. Sulphur always present in the air, 41. " Sulphur rain," 42. Sunsets, gorgeous, 66. Symons, his researches on British rainfall, 151. Symptoms observed at great altitudes, 119. TELEGRAPHING the weather, 145. Temperature, curve of average, 133. at great altitudes, 78. affected by position of the planets, 97. Thames water, free oxygen in, 173. Thermometer, how to observe the, 97. for ascertaining altitudes, 176. dry and wet bulb, 79. " Thunderbolts, "135. Thunder-clouds, 156. Thunder-storms, electric tension in, 49. means of avoiding their effects, 155. Thunder, rumbling of, 167. Tides, atmospheric, 158. Tin and mercury in experiments on air, 5, 6. Torricelli, originator of the baro- meter, 7. Transparency of the air, 38. Transportation of germs, 142. Treeless plains, the air of, 103. Trees, their influence on air of towns, 94. Tropics, air of the, 105. Tunnels of the Alps, 82. U V UREA ferment in street air, 71. Ventilation, 81. Vesicular theory, 122. Viault, Dr., his remarkable dis- covery, 74. Vibration of t}ie air, 53. Virigny, Dr., air and life, 172. Vitality, its increase with that of oxygen, 16. Volcanic action, 11. ash, 66, 69. effects on sunsets, 66. Volcanoes, the air over active, 102. N 194 INDEX. W WARTMANN, Prof. , on a luminous fog, 155. Water, its boiling point at various altitudes, 77. discovery of its composition, 5. sterilized, 142. vapour in the air, 79, 174. Waves of pressure, 111. 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