»40 



NATURE 



\7an. II, 1877 



has to tiaverbc an exttiided surface of cry land, the former, as a 

 rule, even appears as a rainy wind, while the latter, if its course 

 have been long enough, appears as a dry wind ; and if the 

 mountain range be high enough, which the latter is required 

 to rise over, this may, when it has reached the other side, 

 even stream down as a hot, withering wind, the fohn of Conti- 

 nental writers, oa the thirsty regions. If, then, we find in 

 coast districts a greater yearly rainfall than further inwards, 

 or if, on the wmd side of the hills, we find lower snow- 

 lines and further-reaching terminal moraines of the glaciers 

 than on the lee side ; or lastly, if we find successively regions of 

 forests, of steppes, and of wastes, we may easily recognise therein 

 each time an expression of the power of the winds, which, ac- 

 cording as they are abundantly or poorly laden with aqueous 

 vapour, or even quite dry, call forth this variety of geophysical 

 phenomena. 



The ever-moving atmosphere has therefore the most hetero- 

 geneous actions. While it feeds the glaciers and rivers, it causes 

 at the same time a backward prolongation of these to the common 

 source of the water — to the ocean, so as, with its moist breath, 

 to produce everywhere simultaneously a formation of humus, and 

 awake all into life ; and again, where it is otherwise — where it 

 appears as by nature a dry wind, or has been deprived of its 

 freight of water, it brings with it drought and death. In the 

 deserts the flora and fauna, then, have an extremely poor exist- 

 ence ; the rivers no longer flow in a regular course ; they have 

 already been long in retreat, or are still only intermittent in their 

 flow ; the lakes also, when they are to be found in deserts, con- 

 tinually lose, through the constant evaporation, an abundance 

 of water, although they may long have ceased to have an outlet 

 to the neighbouring sea. In many deserts you do not meet with 

 a single brook or pond ; instead of such, you find only dried-up 

 wadis and depressions, while the extensive stretches of waste, 

 covered with salt incrustations and efflorescences, as also the 

 scattered remains of dead animal species of past times, give 

 evidence that these waste and withered regions formerly wore 

 quite a different physiognomy ; indeed, as the fossils and 

 deposits of gypsum and salt testify, must even have been flooded 

 with enormous inland seas. Now, probably (next to solar heat), 

 it was above all, the winds, especially the dry winds, which, 

 acting for a long period of time in the earth's history, dissolved 

 these seas into aqueous vapour, carried them away, and so 

 transformed the former lake bottom, now laid bare, into a waste. 



Second Part. — But the winds are not only an expression for the 

 general circulation of the air and aqueous vapour of the ocean ; 

 they are also a moving agent ipiand mhne not to be under- 

 estimated, since, in their progress, they communicate their own 

 motion to all bodies which are not heavy enough to withstand 

 them. Now, according as, in this way, solid or liquid bodies 

 (especially the waters of the ocean) are put in motion, the 

 mechanical action of the winds is to be considered from two 

 distinct standpoints ; first, its action on the solid land, and 

 second, on the water, and through this again upon the solid 

 land. 



In the first case, it is the conditions of the strata that are con- 

 tinually altered under the action of the winds. It is at one time 

 the snow, at another the salt-dust, at another the vegetable and 

 animal remains, the ashes thrown out in volcanic eruptions, 

 masses of dust and debris, or lastly, sand, that are whirled about, 

 raised, carried miles away, and again deposited. The so-called 

 wind-bedding characterises in every case the formations so pro- 

 duced, or in course of production. We shall cite here only two 

 of the most remarkable examples of this kind of jDOwer in winds. 

 One is the extensive Chinese Loess formation, which, according 

 to von Richthofen's researches, appears to be quite a wind-for- 

 mation ; the other is the progressive dune-formation and dune- 

 shifting on flat sandy coasts. Closer investigations (in this con- 

 nection) of the conditions under which dunes are generally 

 formed, examinations of their form, slope, and strike, and 

 farther, some materials furnished in the narratives of travel of 

 Rohlfs and Dr. Tietze, have enabled the author to form a new 

 theory as to the origin of sandy wastes, but especially to show 

 that, as a rule, they are simply dune-formations on the shores of 

 the former inland lake which has disappeired through evapo- 

 ration. Some examples of sand scratches, sand cuttings, and 

 the devastations wrought by hurricanes, illustrate the further 

 mechanical action of the winds on the dry land. 



Passing to the mechanical action of winds on water, we have, 

 above al), to consider drift-currents (wind-drifts) and the motion 

 of wind-waves. But while the former manifest themselves as 



poweiful fac'.orsof transport, the wind- waves are besides charac- 

 terised by a not unimportant effect in the direction of depth, but 

 more especially by their now land-forming, now land-shattering 

 surge. In this way the waters appear also as the most 

 powerful medium through which the action of the winds is 

 exerted on the solid land. In fact it is the capricious wind-wave 

 that destroys and carries away whole stretches of coast in order to 

 raise somewhere else and lav dry whole areas out of the oceanic 

 depths (sand bars, sandbanks, flat coasts, delta formations, &c.). 

 It is the wind-wave that ever renders active the principle of 

 constant transformation in opposition to that of stability, and seeks 

 to alter the contours of the dry land. Not without reason, then, 

 does El. Reclus remark : — " It is by the movement of the atmo- 

 sphere that we have to explain the form of continents." {C'est 

 par les 7nouvcinents de V attnosphere, qu^il Jaiit expliquer la forme 

 des continents.) 



Third Part. — The winds, finally, produce, in an indirect way, 

 many geological phenomena. According as they influenca ami 

 determine the air-pressure, they cause no.va perceptible swellinj^ 

 out, nowasinkingof some large water surface, as has been observed 

 on the oceans as well as on the North American and the S wiss lakes. 

 Through this influence of air-pressure the winds further appear 

 to affect volcanoes now favourably, now preventively — since 

 also the lava masses in the crater (according to P. Scrope's 

 representation) must be sensitive to atmospheric pressure ; in 

 high pressure finding a greater resistance, and in low pressure 

 rising and breaking out more easily. The firedamp explosions 

 also appear to be favoured by barometric depression. Similarly 

 a certain connection can be demonstrated between the air- 

 pressure and earthquakes. 



Still more evidently are winds seen to exert an influence on 

 earthquakes and volcanic phenomena, when regarded as rain- 

 winds. With a large access of atmospheric water are connected 

 both subterranean deluges and overturnings, and an abundant 

 formation of steam in the heart of volcanoes ; these circum- 

 stances immediately give rise to earth-tremblings, or violent 

 volcanic outbursts and exhalations of steam. 



If the hypothesis of T. R. Mayer, that the trade- winds are the 

 principal cause of terrestrial magnetism, be correct, we must also, 

 finally, ascribe to the winds an important part in the production 

 of electricity. Lyon, Duveyrier, and Rohlfs have observed that 

 the dry desert wind is uncommonly rich in electricity. 



The author, indeed, has, in the course of his researches, given 

 attention especially to the action of the winds in the most recen!; 

 geological periods, and must in the meantime leave to specialists 

 the more definite answering of the question how far tlie traces 

 of action of winds also in the older periods of the earth's history 

 can be followed. It is certain, however, that since in historical 

 geology we have to do with a land flora and fauna, and with the 

 (wrongly) so-.called ocean precipitate, and so with the building 

 up of sedimentary layers, we have so many undoubted proofs of 

 the existence of rain and rivers, and accordingly of that of M'inds. 

 Even when the earth was still a ball of glowing gas — and con- 

 sequently a sort of sun to the moon's inhabitants, we can conceive 

 the wind already acting as a geological agent — with the proviso, 

 indeed, that the theory (of Faye and Reye) which regards the 

 sun-spots as cyclone-like phenomena, or Secchi's view that the 

 temperature of the sun at the sun's equator is higher than beyond 

 the 30th degree of latituie, be verified. 



UNDERGRO UND TEMPERA TURE ' 



A REMARKABLE series of observations have recently beea 

 "^^ taken in a boring at Sperenberg, near Berlin. The bore 

 was carried to the depth of 4,052 Rhenish (or 4, 172 Enghsh); 

 feet, and was entirely in rock salt with the exception of the firsq 

 283 feet, which were in gypsum with some anhydrite. The 

 observations were taken under the direction of Herr Eduard 

 Dunker, of Halle-an-der-Saale, and are described by him in ; 

 paper occupying thirty-two closely printed quarto pages (2o6.« 

 238) of the Zeitschrift fiir Berg-Hictten-und-Salinen'Wesei^ 

 (xx. Band, 2 und 3 Lieterung, Berlin, 1872). 



' Ninth Report of the British Association Committee, consisting of Pro^. 

 Everett, Sir W Thomson, F.R.S, Prof. J. Clerk Maxwell, KR.S., G.J. 

 Symons, F.M.S., Prof. Ramsay, F.R.S. , Prof A. Geikie, F.R.S., James 

 Glaisher, F.R S., George Maw, F.G.S., W. Pengelly, F.R.S , Prof. Hull, 

 F R.S., Prof. Austed, F.R.S., Prof. Prestwich, F.R.S., Dr. C. Le Neve 

 Foster, Prof. A. S. Herschel, G. A. Lebour, F.G.S., andA. B. Wynne, 

 appointed for the purpose of investigating the Rate of Increase of Under- 

 groui d Temperature downwards in various Localities of Dry Land, and 

 under Waie.-. Drawn up by Prof. Everett, Secretary. 



