Recent Science

III. Atmospheric Electricity

WE live in an atmosphere which is loaded with electricity. When heavy storm clouds obscure the sky, and, taking those yellowish tints which are characteristic of electrified vapors, send toward the earth immense sparks of lightning, the electricity in the atmosphere becomes visible. We may also collect it in the way Franklin and Buffon used to collect it, by means of kites launched high ill the air, and study it in the laboratory. Again, when cold weather sets in over the dry plateaus of Siberia or America. the air becomes so permeated with electricity that a fur coat, thrown off in The obscurity, glitters with crepitating sparks. But even in cloudless weather in Western Europe, if the naturalist walks about with a portable electrometer and measures the density of electricity in the air, as Lord Kelvin did many years ago, when he repeated Pouillet's experiments on the sea beach of the Island of Arran, the continual changes in the instrument's indications will show that masses of highly electrified air are continually wafted along by the gentle breezes at a certain' height, and thus transport and distribute electricity in the atmosphere. And, finally, the electrometers which have been installed at many observatories—partly with the hope that their indications would be of some help in the prediction of local storms and rains—show that at every moment of the day the charge of electricity contained in the atmosphere is changing, so that even at two spots situated near to each other the indications of the instruments may vary in the most capricious way. That the electricity which we find in the atmosphere may originate from various sources—from the evaporation of water which is continually going on on the earth's surface, from the unequal heating of superposed strata of air, from vegetation and even from chemical changes, which go on on the surface of the earth—was poin'ed out long since; and the relative importance of these different causes has remained a subject of controversy for the last seventy years ; but it is only now that our ideas upon the whole subject begin to take a definite shape. A few years ago. two Austrian meteorologists, Elster and Geitel, intending- to study the distribution of electricity in the atmosphere at different heights, inaugurated a series of simultaneous measurements at. the observatory which is planted on the top of the Sonn- blick (a high peak of the Tyrolean Alps), and in a valley at the foot of the peak. They had. however, to realize to their regret that their comparative measurements were a failure, because a waterfall which runs in the valley so much electrified the air around it, up to an altitude of 1.600 ft., that no comparison was possible between the low-level and the high-level observations. This unsuccess brought the question as to the electrifying powers of waterfalls again to the front, and Herr Lenard undertook a series of observations on their electrical effects in Switzerland. t It appeared that, tu say nothing of large waterfalls. even the small ones, a few feet high, send into the air considerable charges of electricity, provided they bring down a large amount of rapidly dashing water. The smallest jets of water, which drip on the rock s:des, and even roaring streamlets, have the same effect; while a bove the surfaces of auiet lakes no electrification of the air was de- teeted, notwithstanding the constantly going on of evaporation, In further prosecuting his researches, Lenard came to the conclusion that the current theory which explains electrification in the neighborhood of waterfalls by the inductive action of the positive electricity which is usually spread in the air during fine weather. is not supported by observation. He remarked that neither evaporation nor the mere rushing of water drops through the air would explain the phenomena, and that the chief cause of electrification of the air is the tearing asunder of the drops of wa ter as they fall upon the wet rock surfaces at the bottom of the waterfall. From these shocks electricity originates, and while the surrounding air is loaded with negative electricity, the sprav of water which rises at th e foot of the waterfa 11 i s electrified positively. Laboratory expel'.ments further confirmed this view. The amount of electricity developed by the mere passage of a jet of pure water through air, or when water glides upon an inclined smooth surface, is insignificant. Th e drops must fa 11 upon a h ard wetied surface and break into minute droplets, in order to develop electricity. It appeared, moreover, that a slight addition of common salt to the water was sufficient to totally ! modify the effects, and to electrify air with a positive charge instead of a negative. I Lenard's observations and experiments thus give a new meaning to the experiments by which Lord Kelvin and Messrs. Maclean and Goto lately proved that air, even absolutely dust-free, can be electrified by a jet of water. By letting such a jet run for months Within a vat in verted over a large wooden tray filled with water, so that all possible dust was eliminated, , it was proved that air was electrified. and that it re- I tained its charge for a certain time. * It was also shown ' —and this is of great importance for the knowledge of atmospheric electricity—that the above source of electrification is by no means insignificant. It may be . such as to bring masses of air and cloud into motion with nearly the same energy as they are moved about ! by differences of temperature.! The amount of electricity which is sent in this way into the air is immense, and thus some support is given to the ideas developed by Plants and his follower Dary, and partly Palmieri, who m/tintained long since that atmospheric electricity must be one of the great causes disturbing the equilibrium of the strata of air.J The importance of these facts in the economy of nature is self-evident. The supply of electricity in the air is continually renewed. The waterfalls in the valleys, the splashing of the waves on the shores of the lakes and rivers, and the splash of drops of rain on the ground send masses of negative electricity in the air; | even the watering of our streets and of our plants in j the orchards has the same effect on a limited scale. On the other side, the waves of the sea. as they break against the rocks and fall back in milliards of droplets upon the beach, supply the air with masses of positive electricity, the amount of which rapidly increases after each storm. And when we stand on a sea beach. we not only inhale pure ozonified or iodized air; we are. so to say, surrounded by an electrified atmosphere which. as already remarked by Humboldt and often confirmed since. || must have a stimulating effect upon our nervous activity, as well as upon the circulation of sap in plants. It might be presumed that the generation of electricity which, we now see, takes place when drops of water strike the surface of the rocks, or of water itself, is due to a mere mechanical action; and Lenard (who expresses his views in the old language of the two electric fluids) represents such action in this way : each drop is coated with a double envelope of positive and negative electricity; but when itfalls upon an obstacle, its outer negative envelope is knocked off, and part of the negative electricity goes to the air, while the drop remains laden with a preponderating positive charge.-r However, matters appear to be much more complicated than that. Chemical action, as well as physical action. intervenes, as has recently been proved by Professor J. J. Thomson. Viewing the subject in connection with all his previous work, the Cambridge professor has had the happy idea of extending that part of Lenard's experiments ill which he endeavored to ascertain the effects of water containing different substances in solution being left to drop ' through different gases. It became at once apparent that the chemical constitution of both the drops anCthe surrounding gas was of first importance for the phenomena in question. ** When drops of pure water' were left to fall through an atmosphere of water vapor';"all air having been carefully eliminated from both the water and the surrounding vapor—there was no separation of electricities and no electrification : out the water vapor was electrified as soon as some air was admitted into the vessel. The same occurred when chlorine water dripped through chlorine ; it gave no electrical effects. Electrification was, on the contrary. quite manifest when pure and airless water was dripped through some other gas, e. g., hydrogen, or when weak solutions of various substances were used instead of pure water. With solutions of organic substances, such as phenol, acetic acid, and so on, the electrifying effects were even more apparent. In short, a difference between the chemical composition of the liq uid and the gas through which it dripped was required to produce a disengagement of electricity. Moreover, when the temperature of the dripping water was raised within certain limits, the electrification was rendered still more intense—a great variety of effects being obtained by varying both the substances dissolved and the surrounding gases, and the temperatures of both - The conclusion which Professor J. J. Thomson draws from these most suggestive experiments is of paramount importance for both this special subject and the theory of electricity altogether. The electrification of a gas, in his view. is not a mere mechanical process. It is a chemical or a quasi-chemical process which goes on within the molecules of the Part at least of the molecules of the electrified gas must be split up into atoms, or at least the atoms must be temporarily dissociated as they enter into a new combination, in order to give up electricity. It is therefore the atoms of the gas, not its molecules, which carry electricity : a molecule of a gas, Professor Thomson maintains, cannot be electrified.:J: To tile general reader this distinction between atom and molecule may seem irrelevant; but it touches upon one of the vital questions in the theory of electricity, while it aids us, at the same time, to understand various phenomena which formerly were beset with difficulties. To take an illustration from a more special subject, we may see how Professor Thomson's views help to explain the formation of larger drops in an electrified steam jet. We know that the electrification of a steam jet favors the formation of large drops within the steam : we see it from its sudden change of color under the electrical discharge. But Lord Kelvin showed, some time ago, why it is so difficult for small drops to grow large without the aid either of electricity or dust in the air. The enormous tension to which the water molecules are submitted on the surfaces of the very small droplets results in the immediate evaporation of the latter. As soon as thev have originated, they must die. They may survive only if they find particles of dust round which they may grow—a London fog “being an excellent illustration of the aid given by smoke to the formation of larger drops. Or else electricity must come to their aid. It appears, however, from J. J. Thomson's mathematical treatment of the su bject, that, if electrification were distributed equally through the steam. it could have no such effect. It must be unequally distributed, and this Professor Thomson maintains is really the case, because electricity originates from a number of dissociated and therefore electricallv loaded atoms which are scattered through the space occupied by the steam. Unequal electrification diminishes the surface tensions in small droplets and permits them to grow into larger drops. This is then the process by means of which electricity intervenes in the formation of the heavy yellow tinted clouds which we see when a thunderstorm is coming, and we obtain thus the cue to most familiar phenomena which hitherto it was most difficult to understand. * As to the general bearing of Professor Thomson's ideas, it is sufficient to say that they make part of a great body of doctrine which endeavors now to bring science to consider electricity and chemical action as two moods of the same energy. Immense progress has been achieved during the last fifteen years in the elaboration of this theory, which Helmholtz had so brilliantly summed up in 1881 in a Faraday lecture delivered before the Chemical Society. But. in order that these views should become generally accepted, they must be brought into connection with the dynamic views on electricity developed by Faraday. Maxwell and Hertz, and in his lecture Helmholtz spoke of his intention of so doing. Unhappily, he was lost to science before he had accomplished this great task, and none of his followers has yet undertaken it. Perhaps a greater accumulation of facts and a deeper knowledge of electricity are required before science can be endowed with this further generalization. IV. GEOGRAPHICAL EXPLORATION. Nothing can be more welcome for the future development of physical geography and science generally than the renewal of interest in antarctic exploration which is now witnessed all over Europe. The fiftieth and last volume of the Challenger Reports being now out, and the results of this epoch-making expedition which has so much enriched our knowledge of the oceans and of their physical and organic life being now published in full. the leading scientific bodies of this country have already taken the initiative of a new expedition.f The Royal and the Geographical Societies. as well as the British Association, insist upon the necessity of the vast domain of antarctic seas and continents being explored by a well- equipped expedition consisting of two ships built on purpose for cruising amid the ice. Belgium is already sending out an antarctic expedition. And as to the Swedes, they not only have received with enthusiasm. and at once subscribed the funds for, S. A. Andree's scheme of exploring the north polar regions in a balloon ;:: they also direct their efforts southward. and a nephew of Nordensk- jold starts next autumn for ar,tarctic exploration. Besides, the necessity of antarctic exploration has been fully discussed at the German Geographical Congress in April last, and the International Geographical Congress, which meets by the end of this month at London, will resume the same discussion. And in the meantime a daring Norwegian seal hunter and a Swedish whaler have already made the first steps toward a reconnoitering of the antarctic continent, while a couple of years ago an attempt was made in this country to utilize the cruises of four Scotch whalers for some scientific observations in the same regions. For the last fifty years the exploration of the seas surrounding the south pole has fallen into total neglect. All efforts have been directed toward the north, and since the times of James Ross and Hooker no scientific expedition has cruised in antarctic waters. True, that those who went north ward and wintered in North Greenland, Spitsbergen, and Franz Joseph's Land, or even on the northern coasts of Siberia, returned home with such admirable results that all the temptation was on this side. They brought in Wonderful collections of northern flora and fauna and of fossils, upsetting all current ideas relative to the distribution of climate and organisms. Their notebooks were filled with important observations in all branches of the physics of the globe; and they had to narrate the most fascinating or touching stones of endurance and tenacity of purpose. of successes and privations. When they described the fairy scenes of nature plungedin the arctic night, or awakening under the first rays of the long-missed sun, one understood how deeply impressed they had been by northern nature—what an imperishable love for it they all had brought from the north. Each wintering in those regions not only immensely enriched science, and widened our conceptions of nature, but even the artist returned so much inspired by the melancholy but by no means gloomy northern landscape that we now see Julius Payer, dissatisfied with his own beautiful paintings, starting again with an artistic expedition to the far north, in order to paint that nature on the spot with all its vivid colors and life. * Nothing of the sort is found in the rather dreary journal of the last antarctic explorer, the younger Ross, who spent the three summers ofJ1841-1843 in most wearisome working through the ice pack, and in cruises at the foot of a formidable ice wall, without even daring to land for more than a few minutes on two minuscule islands of the part of the continent which he had discovered. An exaggerated idea of the difficulties 'and uselessness (of antarctic exploration had thus been created in the public mind. This gloomy view is, however, already modified to some extent by the experience gained during the last two years. In November, 1893, the Norwegian seal hunter Captain Larsen, on board the small steamer Jason, approached Graham Land, i. e., the extremity of the antarctic continent which is pointing toward South America, and is separated from it by a distance of only 400 miles. He sailed along its eastern coast, formerly quite unknown, and ascertained its position for full three degrees of latitude, up to the 68th degree. He also found no difficulty whatever in landing twicef—he and his mate having only one regret—that they were on a seal hunting voyage, and not on a scientific expedition, and thus could not have a run inland over the glaciers which flow amid not yet extinct volcanoes. Even Victoria Land, which seemed so inaccessible to James Ross, was visited at Christmas and new year last by the Swedish whaling steamer Antarctic. Following the very track of Ross, the Swedes fought for thirty-eight days their way through the girdle of pack ice which defends the access to Victoria Land, before they reached the ice-free Ross' Sea; and if they went in that sea no further than the 74th degree, it was simply because no whales appearing, they steered back.) On their back journey in the later part of the summer, they even found the ice girdle sufficiently loose to make their way through it in six days. Happily enough, they had a naturalist on board ; that is, to tell things as they were, u. E. Borchgrevink, one of the enth usiastic naturalists whom Sweden owes to its arctic expeditions, wanted by all means to catch a glimpse of the antarctic regions, and as he could not be taken on board the whaler as a naturalist, for lack of accommodation, he went as a simple sailor, and of course, as may well be expected from Torell's and Nordenskjold's countrymen, obtained from the crew every possible assistance for scientific work. From him we know that no difficulty whatever was found in landing, first oil Possession Island—the very island upon which Ross landed only to take a nominal possession of the discovered land— and next at Cape Adare, on the mainland, which never before had been trodden upon by man's iuot. We may thus feel sure that the explorers of these new grounds will find no greater obstacles in their way than those which have been successfully over come by so many aretic travelers. And if the aim of the expeditions is not a race for beating the record in tlie approach to the pole, but scientific exploration, the experience of the Swedish expeditions, as well as ol Parry and John Ross, is there to prove that the greatest scientific results can be, and usually are, achieved without having losses of human life to de pi ore. That a scientific exploration of the antarctic regions would immensely increase our knowledge in nearly all branches of physical geography, meteorology, biology, and so oil, is almost self-evident.§ The Challenger expedition has shown how knowledge can be increased through the careful exploration of pretty well known regions, while in the far south every step would be made on a nearly quite un broken ground. But there are certain problems of science, of exceptional importance under the present state of knowledge, which can only be solved in the southern circumpolar regions— nowhere else—and which deserve a special mention. One of them—the necessity of a magnetic survey—has been fully treated by Dr. Neumayer,|| and by the Antarctic Committee of the Royal Society. As is well kaown, an exact knowledge of the position which the magnetic needle assumes at every spot of the earth's surface—that is, of the angle it makes with the meridian and the horizon—as well as of the force with which it is attracted in the direction of the magnetic poles, is of the first necessity both for the theory of earth magnetism and for the practical requirements of navigation. Special magnetic maps, based on as large a” possible a number of direct observations, are calculated and drawn for this purpose, and many physicists —Dr. Neumayer, Captain Creak, Professor A. W. Rucker, H. Wilde, and many others—have lately taken great pains in reconstructing anew, for the w hole of the earth's surface, or for large portions of it, the magnetic maps which had been constructed by G:auss in 1839. However, all these investigations meet with one hitherto insuperable ohstacle. We know well the elements of terrestrial magnetism for the northern hemisphere, as also for the southern hemisphere as far as the fortieth degree of latitude ; but beyond this line we have an immense gap— 3,500 miles each way from the south pole—which can be filled by no amount of mathematical speculation. More than fifty years ago Ross made a magnetic survey of the antarctic .seas; but his data are 110 longer available, because it is now known that the variation in terrestrial magnetism, which takes place from year to year, proceeds very irregularly in many localities ; * we know that changes have taken place in the magnetic elements south of the 40th degree of latitude, but there is no means of ascertaining with any accuracy the extent of these changes.^ It is evident that nothing short of a new magnetic survey of the antarctic regions can remedy this evil, or give the necessary data for revising the current theory of revolution of the magnetic poles, which badly needs revision. To u»e Dr. Neumayer's words, without such a survey '"it is an utterly hopeless case to strive with prospects of success at the advancement of the theory of the earth's magnetism." The same is true as regards the modern investigations into the exact shape of the earth. Formerly we could be satisfied with representing the earth as a ball slightly flattened at its poles, the flattening being supposed to follow the curve of an ellipse. But now geo- desists discover that the earth ball has considerable irregularities of shape, both local and general, toward the poles; and as the earth's diameters are the basis of all measurements in astronomy, they spare no efforts to measure aecurately these irregularities. Precise methods were lately elaborated for utilizing pendulum swingings as a rapid and sufficiently exact means for measuring the local deviations in the earth's surface from the ideal shape. But all efforts stumble against the absence of data from the southern hemisphere. Seven pendulum measurements are all that we have beyond the fiftieth degree of southern latitude. and none was ever made within the antarctic circle. Three or four pendulum observations in Graham and Victoria Land would. therefore, be of a much greater value for geodesy than ten times as many ohservations elsewhere. Besides we know that the earth's crust is not quite rigid, and there are good reasons to suppose that it yields to a certain extent under great accumulations of alluvial deposits. as well as of ice and snow.) such sinkings being possible causes of submergence of large continental areas. But, again, the only means of ascertaining in how far these views are correct is to make a series of pendulum observations in different parts of the antarctic continent. And, finally, there is the immense question as to the origin of the present floras and faunas and their relations with the distribution of plants and animals during the tertiary age, which now excites naturalists, and again can only be solved by an exploration of the antarctic continent. This latter question is so important in itself that it cannot be treated here incidentally, and may best be discussed separately on some future occasion. Its sii bstance. however, and its bearing upon antarctic problems can be indicated in a few words. It is well known that the present floras of different portions of the earth offer such peculiarities, both in the plants which they possess in common and in those which they differ in, that, after having paid a tribute to different hypotheses, naturalists came to look for the origin of the present floras .of Europe, America and Asia in the rich vegetation which covered the aretic and sub-arctic zone during the tertiary period. The thousands of specimens of tertiary vegetation which have been unearthed from the peat bogs of Greenland, Spitzbergen, New Siberia, and so on, leave not the slightest doubt about the north polar archipelagoes having” been covered during the miocene period with trees and herbaceous plants, which must be considered as the ancestors of the plants now covering Europe. America and Asia. We find the flowers and the fruits of these trees, shrubs and herbaceous plants in the peat bogs of the far north, and we unearth the very insects which fertilized the flowers. From this flora, which was repulsed to the warmer zones during the glacial period and afterward partially reconquered its former abodes after glaciation was over, all our present floras of the northern hemisphere originate. So much may be taken as granted. But a series of recent researches have brought naturalists to inquire whether there was not, during the tertiary age, an expansion of land in the antarctic zone as well; whether what is now a dreary desert of ice, amid which high volcanoes only give sign of life, did not also enjoy a warm climate, and was not the land wherefrom the present vegetation of the southern extremities; of our continents has originated. This very difficult question, which Darwin was inclined to answer in the affirmative, is now the subject of an animated controversy among naturalists ; but it is evident that it will receive no definite solution so long as we remain completely in the dark as to what the antarctic continent was during the tertiary age. Some time ago the prospects of finding traces of tree vegetation in these frozen regions were extremely small. Hooker saw no traces of vegetation on the barren rocks of Victoria Land, and we now learn from Borchgrevink that the discovery of one single lichen on Cape Adare already filled his heart with joy. § However, oil the other extremity of the antarctic continent Graham Land seems not always to have had the same barren aspects as it has now. No sooner had Captain Larsen set his foot on Seymour Island (at the northern extremity of Graham Land) than he was struck with the amount of petrified wood which was scattered about; and it appears from the specimens of fossil coniferous wood and shells he has brought home that both probably belong to the lower tertiary period. || This discovery alone is sufficient to raise the best hopes as to the possibility of finding the cue to the floras of the southern hemisphere in the icy deserts of the ant arctic continent; and if such discovery is really made, it will settle at once a grave problem which naturalists might discuss for years without coming to any definite solution. We thus have' three important problems, in geodesy, earth magnetism and geographical distribution of plants and animals, which cannot be solved otherwise than by an exploration of the lands situated within the antarctic circle ; and several problems of less importance might be mentioned in addition. But we need not further dwell upon the scientific aspects of antarctic exploration (which are sure to be fully discussed by the end of this month at the Geographical Congress), the more /'lo as there is one more remark to be made. Those who have followed the development of aretic exploration for the last thirty years, since it took a thoroughly scientific character in the Swedish expeditions to Spitzbergen. must have been struck by the deep influence which these expeditions have exercised in Scandinavian lands upon the growth of science and the development of taste for science altogether in wide circles. Swedish and Norwegian science (which by no means receives in West Europe the attention it really deserves) may be considered without exaggeration as a daughter of the Spitzbergen expeditions and of Nor- denskjoid's journeys in search of the northeastern passage. The names of Swedish and Norwegian scientific men which are well known at the present time to every student of science are all names long since familiar to the readers of arctic literature; they appeared for years past, either among the members of those expeditions or among persons who took part in the scientific discussion of their results. Quite a phalanx of men of science has grown out of these expeditions. And at the same time a general interest in and a remarkable taste for scientific research have been widely spread in the two countries. The admirable popular account of the Spitzbergen expeditions and their scientific work, written by Chydenius, was read far and wide in Sweden and Norway. It was—we know it—a most popular book among the whalers and seal hunters, and they have react it with profit, as may be seen from the services they ha ve rendered in the discovery of the northeastern passage. Before the year 1870. all Russian geographers were persuaded that the Kara Sea, which lies between Novl1ya Z;mlya and the Siberian coast, on the way to the Siberian rivers, was quite impracticable on account of the ice with which it is stocked. It was kn:wn to us as 'the ice cellar.” But that year a Norwegian whaler, Captain Johannesen, peeped into the Kara Sea, and finding the entrance free, he steered straight forward and cruised in the ice cellar without incumbrance. Next year half a dozen small Norwegian schooners rushed into the newly opened sea, aud, as their captains were already aware of the importance of arctic exploration, in eonsequence of the wide interest in that sort of research which was spread by the Spitzbergen expeditions, Mobn, Nurdenskjold and Peter- mann found no difficulty in instructing them in what had to be done. In one summer the Kara Sea, which had not been navigated for the last three hundred years, was explored in all directions; soundings and surface temperature measurements were taken ; the wintering place of Barents, at the northern extremity of Novaya Zemlya, which had not heen revisited since the sixteenth century, was reached ; and one or two seal hunters dashed eastward, saw an open sea, and proved the possibility of easily reaching the Obi. The northeastern passage was rediscovered, and Norden- skjold at once found support in his country for reaching twice the mouth of the Yenisei, and finally, for circumnavigating Asia. Never. in any other country of the world, did science, spirit of adventure and commercial pursuits so admirably well go hand in hand. In no other country would that have been possible, not even in Scandinavian lands, before the Spitzbergen expeditions took place. And now it is certainly not a simple coincidence that the first steps toward the exploration of the antarctic seas and continent have also been made by Norwegian and Swedish whalers. In fact, one cannot read Larsen's journal, simple as it is, nor witness Borchgrevink's enthusiasm, and Svend Foyn's enterprise, in manning the Antarctic, without realizing that a whole atmosphere of interest in arctic matters and taste for them was created on the Scandinavian peninsula by the .scientific exploration of the arctic regions —an interest which, so far as the last few years' experience goes, seems not yet to exist among Scotch whalers. For science, antarctic exploration will prove invaluable. As to society at large, it has all to win if the spirit of enterprise is directed toward regions where there are no natives to conquer, but where there is very much to endure for a disinterested purpose, and so immensely much to be learned about the physical life of the globe under all its aspects. P. KROPOTKIN.

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