Sept. 13, 1877] 



NATURE 



419 



attention to the subject and either confirm or disprove facts 

 which, if true, would seem to afford a crucial test of the truth 

 or falsehood of some of the most important theories of modern 

 geology. 



The fact which I assert is, that there are no traces of glacial 

 action, or of raised sea-beaches in Orkney. 



I speak from an intimate personal acquaintance with these 

 iiiands, which arc my native county, and almost every yard of 

 whose surface and shores I hive explored with rod and gun, and 

 in the course of canvassing at elections, and for many years back 

 keeping a special eye on this very subject. Now I can assert 

 positively that I never saw a boulder or perched block, or the 

 trace of any till, boulder clay, kame, eskar, raised beach, or 

 other form of glacial or marine action. 



The whole of the islands consist — except a small patch of 

 gr.mitic axis — of Devonian strata, bare in pUces, but for the 

 most part covered with a mantle of soil, which is the obvi >us 

 result of the disintegration of the subjacent rock by existing sub- 

 aerial causes, such as wind, frost, and rain. 



In places, where soft strata come to the surface, this soil is 

 deep and clayey, and the sections of it, afforded by the coast- 

 line, might readily be mistaken at a distance, or by a super- 

 ficial observer, for boulder-clay. But a close examination will 

 show that the stones in this stony clay are always angular and 

 always similar to the adjoining strata, and that the larger stones 

 are generally deposited, allowing for subsidence and displace- 

 ment, in the original lines of stratification conformable to those 

 of the unworn rock below them. A good example of this may 

 hz seen withm 2Co yards of Kirkwall, on the east side of the 

 bay under Crorai\eU s old fort. 



Let any one compare this with the section of glacial boulder- 

 clay shown on the other side of the Pentland Firth at Scrabster, 

 and he does not require to be a geologist to understand the 

 difference between a surface soil of gla;ial deposit and one of 

 disintegrated rock. 



In like manner I have ob.erved innumerable sections of surface 

 soil and of mounds and ridges, which at first sight might have 

 passed for marine or glacial, and I have invariably found them 

 to consist of angular fragments of the subjacent rock passing 

 on the one hand into thoroughly decomposed rock or soil, and 

 on the other into the solid strata on which they rest. 



I beliei'e I may state broadly that there is not a rolled or 

 rounded stone or pebble, or trace of sand or gravel, in all 

 Orkney above the level of the present sea-beach and blown 

 sands, and away from the beds of the existing lakes and small 

 streams. 



There is not the vestige of a raised beach along the hundreds 

 of miles of rocky coast of the various sounds and islands, or in 

 the many sheltered inlets where, in the nearest counties of 

 Scotland such as Sutherland, Ross, and Cromarty, raised beaches 

 are invariably seen. All recent movements seem to have been 

 movements of subsidence and not of elevation. The Loch of 

 Stennis, with its surrounding plain, affords conclusive proof that 

 al no recent geological period can the level of the sea have stood 

 higher relatively to that of the land than it does at present. Had 

 it done so the Loch of .Stenn^s, which is nosr exactly level with 

 the sea so that the tide Hows into and out of it, must inevitably 

 have been a sheltered inland fiord of salt water extending to the 

 hills which bound the plain, which as the land rose or the sea 

 retreated, must have left the plain covered with sand, shingle, 

 and marine or brackish shells, of none of which is there the 

 slightest trace, but, on the contrary, the ordinary rock strata 

 with their disintegrated surface soil, occupy the whole plain and 

 come up to the margin of the exis'ing loch. 



Now as to the inference from these facts. 



The received theory of most glacialists is, that during the 

 glacial period there was a great polar ice-cap extending over the 

 whole of Scandinavia, .Scotland, and a great part of England 

 and Ireland. As a corollary of this many draw the inference 

 that such an accumulation of ice, by displacing the earth's centre 

 of gravity, would raise the level of the sea in the Northern 

 hemisiihere, and thus account for the higher levels relatively to 

 the land at which it has undoubtedly stood. 



Others contend that the glaciation was more limited and only 

 extended in islands as it were, round each considerable mountain 

 group in northern latitudes, and these attribute the phenomena 

 of raised beathi:s, &c., to local elevations of the land rather th n 

 to general elevation of the sea. 



Now here appears to me to be an opportunity of applying the 

 experifneutitiii cnicis to these two conflicting theories. 



If it be true that Orkney is not glaciated, and has no raised 



beaches, it seems to follow that the second, and not the first, of 

 these theories must be the true one. 



The second theory would account perfectly for the boulder- 

 clay being found in Caithness, over the plain of which we may 

 easily suppose the glaciers from the great mountain range which 

 bounds it on the south and west, to have extended as far as 

 Scrabster and the south shore of the Pentland Firth, while in 

 Orkney there were no glaciers, because there was no great local 

 mass of mountain region to produce them. 



But, on the theory of a great ice-cap, I cannot see how 

 Orkney could faU to have been planed by ice and covered by 

 boulders, perched-blocks, and masses of glacial clays, sands, 

 and gravels. 



In any case the absence of raised beaches and of all traces of 

 marine action above the present sea-level, seems to be inconsistent 

 with any theory of a general and uniform rise of the ocean in these 

 latitudes. 



As regards the Shetland Islands I cannot speak with the 

 same confidence, not being so intimately acquainted with them ; 

 still, having travelled over a great part of the principal islands, 

 and coasted along their shores, I can assert that I have never 

 seen any traces of glacial action, or of raise! beaches. The 

 latter must, I think, inevitably have shown themselves in the 

 form of sea-caves at a higher level, such as those at Cromarty, 

 had they ever existed, as the present line of exposed rocky coast 

 is worn by the waves into innumerable caves and clefts. 



As to boulders or boulder-clay, I do not believe they exist, 

 and the only rouaded or water-worn stones I have ever seen 

 have been rolled in the Devonian and not in any modern seas, and 

 result from the surface disintegration of the great conglomerate. 



These are abundant in exposed situations, and they show the 

 necessi y for care in inferring modern glacial or marine action 

 fiom the presence of rolled stones of foreign rocks. 



In conclusion, I believe that these groups of islands, Orkney 

 and Shetland, have never been subjected to glacial action or 

 suljmerged and subsequently elevated, in any recent geological 

 period, and that these facts are inconsistent with any theory of 

 a great polar ice-cap, or of any uniform rise of the level of the 

 ocean in northern latitudes. S. Laing 



Brahan Castle, Dingwall, N.B., August 25 



Meteorological Effects of Eclipses 

 In connection with certain variations of temperature observed 

 during the total eclipse of the moon on August 2+, 1877, by M. 

 Berigny, and discussed at a late meeting of the French Academy 

 of Sciences, as reported in Nature (vol. xvi. p. 412), I am 

 reminded of some observations made on board H. MS Challciigei- 

 during the total eclipse of the sun on April 6, 1875. Tlie position 

 of the"ship at noon of the day of the eclipse was in lat. 27° 13 N., 

 Ion". 137° 59' E. about 400 miles south of Japan and 200 miles 

 due°west 01 the Bonin Islands. If my memory be correct, the 

 eclipse was only partial for the part of the world we were in, a 

 portion of the sun's disc being still v.sible in the shape of a thin 

 crescent at the moment of maximum obscuration. The eclipse, 

 occurred in the afternoon, and was heralied by a breeze from 

 the south-west, which continued during the rest of the evening ; 

 but what at the time struck us as very remarkable was the lact 

 that it was accompanied by a rise of the surface temperature 

 of the sea, as will be seen from the following observa-ions ma.,e 

 at the time : — 



The Challo!;^, progressing at the rate of about three kiots pei 

 hour, had just entered an area of alternate streaks of warm and 

 cold water, the former due to the North ^^<^f<'.^f^'°J'^l 

 current, knoavn as the Kuro-Siwp or Japan current, the latter to 

 the Arctic current which ilows,down off the east coast of iNipon, 

 so that the observed rise of ti;mperature, and P'^^^aps a so tne 

 south-westerly breeze which sprung up at the c^'^'^f"':^}^;"; °' 

 the eclipse may be a mere coinci(ieuce, and 1 give tne ouse 

 tlons for phat they are worth. 



