August 29, 187SJ 



NATURE 



475 



been described by Mr. Charles Richardson, its engineer, to 

 Section G, at the Bristol meeting in 1875. Ii^ June, 1878, the 

 trial heading had been driven more than half-way under the 

 Severn, and the most difficult part had been overcome. In the 

 opinion of the engineer, the water in the tunnel springs — one of 

 which had yielded 300 gallons per minute — was not Severn 

 water, but derived from springs in the pennant and other strata, 

 and the salt from the occasional beds of salt in the Bristol coal- 

 field. The author had analysed water from four springs, and 

 compared the results with those from Severn water at various 

 times of the tide, and with water from wells on the English side 

 sunk forty feet through the alluvium. The results were arranged 

 under the heads of specific gravity, total solid residue, and total 

 chlorine per cent. The author found it difficult to avoid the 

 conclusion that the water in the springs was chiefly Severn 

 water. 



SECTION C— Geology. 



The Geological Relations of the Atmosphere, by T. Sterry Hunt, 

 LL.D., F.R.S. — The author began by noticing the inquiries of 

 Ebelmen into the decomposition of rocks through the influence 

 of the atmosphere, resulting in the fixation of carbonic acid and 

 oxygen, and discussed the question at length, with arithmeti- 

 cal data. He inquired farther into the fixing of carbon from 

 the air by vegetation, with liberation at the same time of oxygen 

 both from carbonic acid and from the decomposed water, the 

 hydrogen of which, with carbon, forms the bituminous coals and 

 petroleums. It was shown that the carbonic acid absorbed in 

 the process of rock-decay during the long geologic ages, and 

 now represented in the form of carbonates in the earth's crust, 

 must have equalled, probably, two hundred times the entire 

 volume of the present atmosphere of our earth. This amount 

 could not of course exist at any one time in the air ; it would, at 

 ordinary temperatures, be liquefied at the earth's surface. Whence 

 came this vast quantity of carbonic acid, which must have been 

 supplied through the ages ? The hypothesis of Elie de Beau- 

 mont, who supposed a reservoir of carbonic acid stored up in 

 the liquid interior of the planet, was discussed and dismissed. 

 The gas now evolved from the earth's crust from volcanic and 

 other vents was probably of secondary origin, and due to car- 

 bonates previously formed at the surface. 



The solution of the problem offered by the author is based 

 upon the conception that our atmosphere is not terrestrial, but 

 cosmical, being a universal medium diffused throughout all 

 space, but condensed around the various centres of attraction in 

 amounts proportioned to their mass and temperature, the waters 

 of the ocean themselves belonging to this universal atmosphere. 

 Such being the case, any change in the atmospheric envelope of 

 any globe, whether by the absorption or the disengagement of 

 any gas or vapour, would, by the laws of diffusion and static 

 equilibrium, be felt everywhere throughout the universe, and the 

 fixation of carbonic acid at the surface of our planet would not 

 only bring in a supply of this gas from the worlds beyond, but 

 by reducing the total amount of it in the universal atmosphere, 

 diminish the barometric pressure at the surface of our own and 

 of all other worlds. 



This conception of a cosmical atmosphere, of which our own 

 forms a part, is not new, but was put forth by Sir William R, 

 Grove in 1843, and is developed in the very learned and inge- 

 nious work of Mr. Mattieu Williams, on " The Fuel of the 

 Sun," and has lately been noticed by Dr. P, M, Duncan in its 

 geological bearings, Ebelmen, in 1845, pointed out that the 

 greater weight of an atmosphere charged with carbonic acid 

 would increase the temperature due to solar radiation at the 

 earth's surface, and greatly modify atmospheric phenomena. 



Tyndall, by his subsequent researches on radiation, showed 

 that certain gases, in amount too small to affect considerably 

 the barometric pressure, might influence powerfully climatic 

 conditions, and suggested that in the former presence in the 

 atmosphere of moderate quantities of a gas like carbonic acid, 

 might be found a solution of the problem of the climates of 

 former geologic ages. According to the author, the amount 

 of this gas, which, since the advent of life on our earth, has 

 been subtracted from the universal atmosphere, although it may 

 not have sufficed to diminish by more than a small fraction the 

 pressure at the earth's surface, would account for all the con- 

 ditions of geological history so far as temperature and climate 

 are concerned. 



He maintains that while we have evidence of a warm or sub- 



tropical climate prevailing over the Arctic regions from the 

 carboniferous down to lower cretaceous times, and a gradual 

 refrigeration up to the temperate climate of the miocene age, 

 we had for the first time in the pliocene age the evidence of 

 Arctic cold, which, with some variations, has continued until 

 now. Since that date geographical variations have caused, and 

 may again cause local climatic changes of considerable magni- 

 tude. But no such changes could permit the existence over 

 continental areas within the Arctic circle, of such tropical 

 vegetation as we know to have once flourished there. Geo- 

 graphical changes, 'as J. F. Campbell, Dawson and others have 

 so well pointed out, might lift large areas into the region of 

 perpetual frost, and thus give rise to local glacial phenomena, 

 and may, moreovei', account for considerable local climatic 

 variations at the sea-level since the pliocene age. We cannot, 

 however, account in this way for the warmer climates of previous 

 ages, but must seek for their cause in the former constitution of 

 the atmosphere. 



Touching the suggestion that former climatic changes were due 

 to a displacement of the earth's axis of rotation, the author 

 expressed the opinion that it is irreconcilable with the fact long 

 ago insisted upon by him that "the direction of the Arctic 

 ciurents, Avhich are guided by the earth's rotation, appears, from 

 the distribution of marine sediments, to have been the same 

 since very early periods." Dawson has reinforced this argument 

 by recalling the fact that the southward migration of successive 

 floras shows, in like manner, that from the Devonian age the 

 general courses of oceanic currents, and consequently the posi- 

 tion of the earth's axis, have not changed. 



On the Filtration of Sea-water through Triassic Sandstone, by 

 Isaac Roberts, F.G.S. — Mr. Roberts stated that he was led to 

 investigate the effects produced on sea-water by filtration, in 

 consequence of the constantly-increasing salinity of the water 

 drawn from several wells in Liverpool which are sunk below 

 the sea-level in the Bunter sandstones of that locality. He 

 found that one of the wells, which he selected as the type of 

 the rest, yielded water which increased in salinity at the rate of 

 4*91 to 5'8l per cent, annually, and inferred that the sandstone 

 rock had the power of removing salts out of sea-water. To 

 prove this he filtered sea-water through blocks of the sandstone, 

 and found the inference to be greatly borne out by the results 

 of his experiments. Two cubic feet of the stone removed from 

 the first filtrate of 3J fluid ounces of the water 8o"8 per cent, 

 of the salts held in solution, and each measured quantity of four 

 ounces, which were afterwards filtered through, regularly showed 

 an increase of the salts in solution, until 93I fluid ounces had 

 filtered through the stones. Then these ceased to be operative 

 as filters, and the waters passed through unchanged. After 

 allowing the stones to dry he passed spring water through them, 

 and found that the salts which they had taken up were again 

 removed and washed out, thereby showing the action to be 

 mechanical. 



New Geological Map of India.— Mx. W. Ball,_ M.A.,, pre- 

 sented and explained a new geological map of India which will 

 shortly be published, with a manual. He mentioned that there 

 were 8,000 square miles of coal measures in India, It was of 

 an inferior character, and was unfortunately in the most inac- 

 cessible part of the country. 



Mr. W. H, Baily, M,R.I,A., F.G,S., read a paper On some. 

 Additional Labyrinthodont Amphibia and Fish from the Coals of 

 farrow Colliery, near Castlecotner, County Kilkenny. — These 

 fossil remains, which were found below a bed of coal three feet 

 in thickness, were all impressed on the true coal, and had, in 

 fact, turned into carbon. One of them, which was alnaost per- 

 fect — Megalichthys hibberti — was three feet seven inches in length. 

 This one locality had yielded a larger number of these fossils 

 than all the other coal-fields in Europe. 



On the Ancient Volcanic District of Slieve Gullion, by Joseph. 

 Nolan, M.R.I.A., Geological Survey of Ireland.— Slieve Gul- 

 lion is a mountain situated some few miles north of Dundalk» 

 west of the hilly country lying between the bays of Dundalk and 

 Carlingford. The rocks which mainly compose it are of a 

 plutonic character, consisting of dolerites and elvanites, and have 

 been erupted through granite of lower Silurian age, probably 

 about the close of the palaeozoic epoch. On the west and soutk 

 of the mountain the elvanite forms a dyke-like ridge when it 

 changes from a granitoid rock to a felstone porphyry. Simul- 

 taneously with this change, suggesting conditions of less 

 intense heat and pressure a remarkable fragmentary rock 

 makes its appearance. It is here almost altogether composed 



