48o 



NA TURE 



[September 17, 1891 



in these strata. These, the oldest relics of life yet known, have 

 excited a vivid desire in the Geological Survey to discover 

 further and more determinable fossils associated with them in 

 the same primaeval resting-place. We shall spare no pains to 

 bring to light all that can be recovered in the North west High- 

 lands of a pre-Cambrian fauna." 



In the other paper the Director-General dealt with some 

 recent work of the Geological Survey in the Archaean gneiss 

 of the North-west Highlands. " For some years past," 

 he remarked, "the officers of the Geological Survey have 

 spent much time and labour upon the investigation of the 

 old or fundamental gneiss of the North- west Highlands. 

 They have succeeded in showing that it consists mainly of 

 materials which were originally of the nature of eruptive 

 igneous rocks, but which by a long succession of processes 

 have acquired the complicated structures which they now 

 present. No evidence of anything but such eruptive rocks had 

 been met with until the mapping was carried into the west of 

 Rosshire. In that area it had long been known that the gneiss 

 includes some mica-schists and limestones which were generally 

 believed to be integral parts of its mass. With the accumulated 

 experience of their work farther north, my colleagues were 

 naturally pre-disposed to accept this view, and to look on even 

 the limestones as the result of some crushing down and re- 

 formation of basic igneous rocks containing lime-silicates. But 

 as they proceeded in their work they encountered various diffi- 

 culties in the acceptation of such a theoretical explanation. In par- 

 ticular, they found that with the mica-schist were associated quartz- 

 schists and graphitic schists, and that the limestone occurred in 

 thick and persistent bands with included minerals like those found in 

 the Eastern Highlands in districts of contact-metamorphism. The 

 microscopic examination of some of these rocks showed them 

 to present close affinities to certain members of the crystalline 

 series of the Eastern and Central Highlands, which can be 

 recognized as consisting mainly of altered sedimentary strata 

 (Dalradian series). Yet the officers of the Survey could not 

 separate these doubtful rocks from the surrounding gneiss. The 

 several materials seemed to pass insensibly into each other in 

 numerous sections, which were examined with great care. 

 Within the present month, however, one of the members of the 

 staff, Mr. C. T. Clough, who has been specially engaged in this 

 investigation, has obtained what may prove to be conclusive 

 evidence on the subject. He has ascertained that the main 

 bands of graphitic schist occur evenly bedded in an acid mica- 

 schist, in which, also, thin graphitic layers are distributed at 

 intervals of an inch or less. These rocks are sharply marked 

 off from the true gneiss, though, where they actually join, they 

 appear to be, as it were, crushed along a line of intense move- 

 ment. Mr. Clough and his colleagues are at present disposed 

 to believe that these schists are really an older series of sedi- 

 ments, into which the original igneous rocks now forming the 

 gneiss were erupted. If they succeed in demonstrating the 

 correctness of this inference, they will have established a fact 

 of the highest interest in regard to the geological history of our 

 oldest rocks. Already they have shown the thick masses of 

 Torridon sandstone to be an accumulation of sedimentary 

 materials of pre-Cambrian age. They will push back the geo- 

 logical record to a still more remote past, if they can establish 

 the existence of a yet more ancient group of sedimentary strata 

 among which layers of graphite and beds of limestone remain 

 to suggest the former existence of plant and animal life." 



The session on Monday was opened by Sir K. S. Ball with 

 a paper on the cause of an Ice age. This communication 

 stated that the author had a work in the press dealing with the 

 question of glacial climates. He had revised Herschel's figures, 

 on which Croll's deductions were based, and discovered an 

 arithmetical error of considerable consequence. If 63 repre- 

 sents the number of heat- units received by any hemisphere 

 during summer, its winter receipt will be represented by 37. 

 Consequently, during a period of high eccentricity the 63 units 

 of heat may be received in 199 days or in 166 days, according 

 to the position of the equinoxes, producing either a long and 

 cool summer or a short and intensely hot one. The paper did 

 not deal with geographical considerations, and advocated the 

 occurrence of clusters of alternate glacial and interglacial periods 

 at each phase of high eccentricity in the earth's orbit. This 

 paper excited considerable discussion, in which Prof SoUas, 

 Prof. Wright (of Oberlin, Ohio), Mr. Hall, Dr. Crosskey, Dr. 

 Hicks, and many other glacialists took part. 



Dr. Crosskey followed with his Report on the Distribution of 

 Erratics in England and Wales, in which he referred to the useful 

 work done by the North of England Boulder Committee, in 

 systematically surveying the north in search of boulders and 

 groups of boulders. Details were ^iven of boulders from Lan- 

 cashire, Cheshire, Derbyshire, Staffordshire, and Yorkshire, and 

 it was remarked that boulders were being destroyed so rapidly 

 that many described in former reports had totally disappeared. 

 In another paper the same author controverted a statement of 

 Forbes with regard to the glaciation of the Dovrefjeld. Wherever 

 the basement rock is to be seen, it is glaciated, although morainic 

 deposits were swept away and redistributed by torrential action 

 at the close of the Glacial period. 



Prof. Wright read a most interesting paper on the Ice age 

 of North America and its connection with the appearance of 

 man in that continent. The glacial deposits, transported from 

 I several centres mostly outside the Arctic circle, and the absence 

 of a Polar ice-cap, militated against an astronomical, and for a 

 geographical, cause of the great cold, particularly as an uplift 

 of the glaciated area was coincident with an important subsid- 

 ence in Central America. The author regarded the so-called 

 "terminal moraine of the second period" as a moraine of retreat 

 due to the first glaciation, and thought the evidence of forest 

 beds, mainly to the south of the area, indicated local recessions 

 of ice, and not a single great interglacial epoch. Palaeolithic 

 remains similar to those of the Somme and Thames have been 

 found in several gravel terraces flanking streams which drain 

 from the glaciated region, and made up of glacier-borne detritus ; 

 they are regarded by the author as deposits of the floods 

 which characterized the closing portions of the Glacial period. 

 , The recession of the falls of Niagara and St. Anthony gives an 

 ' antiquity of not more than 10,000 years to the end of the Glacial 

 j epoch— a conclusion supported by the enlatgement of post- 

 I Glacial valleys and the silting up of small post-Glacial lakes. 

 Other papers read on this day were : one by Dr. Hicks, who 

 produced specimens of boulders from Pembrokeshire, which 

 i seemed to him like North Welsh or Irish rocks — his picrite 

 was, however, recognized as an Irish rock by geologists in the 

 room, and in any case a flow of ice down the Irish Sea and over 

 j Pembrokeshire seemed to be clearly proved ; one by Mr. Ken- 

 dall, on a glacial section at Levenshulme, Manchester, in which 

 I he gave evidence from the striation of the subjacent rock, and 

 the intrusion of tongues of boulder-clay into it, the transport of 

 j fragments, the orientation of large boulders, and the direction 

 of striae, together with a consideration of the levels of the dif- 

 t ferent portions of the rock beneath, that the district had been 

 ] traversed by land ice coming from a direction a few degrees 

 north of west ; and one by Mr. Bolton on a group of boulders 

 1 from Darley Dale, near Matlock, which he regarded as having 

 I been washed out of rocks skirting the valley. In connection with 

 these papers may be mentioned a report by Mr. Harrison, who 

 has excavated in the talus under some rock-shelters at Oldbury 

 Hill, near Ightham, from which he obtained forty-nine well- 

 finished Palseolithic implements and over 600 waste flakes, which 

 were described in a separate paper by Prof. Prestwich. Prof. 

 Wright gave also a brief account of the basaltic lava beds of the 

 Pacific coast, which are of post-Tertiary age. New evidence in, 

 favour of the genuineness of the Calaveras skull and other 

 I human remains found under the lava beds was given ; and the 

 discovery of a small clay image in a similar position under the 

 western edge of the lava plains of Idaho at Nampa was re- 

 corded ; the lava beds are correlated with the glacial deposits of 

 the East. 



Mr. Jones's report on the Elbolton cave, near Skipton, was of 



unusual interest. Long-headed human skulls were found with 



burnt bones and charcoal in the upper stratum, associated with 



I domestic animals and pottery ornamented with diamond and 



I herring-bone patterns ; while at a much lower level — 13-15 feet 



I below the floor — there were round skulls, much more decayed, 



i in connection with ruder and thicker pottery than has been 



I found in any other part of the cave. No flints or metal of any 



kind have been found, and bone pins and other worked bones 



are the only human implements hitherto discovered. The 



remains of bear and hare have been found in cave earth below 



this level, and the investigation is to be continued in the hope 



that remains similar to those of the Ray Gill fissure may yet be 



met with. 



An interesting discussion was raised on the paper by Dr. 

 Hicks on the Silurian and Devonian rocks of Pembrokeshire 



NO. I 142, VOL. 44] 



