574 



NA TURE 



[Oct. 13, 1887 



directly south from Pau in Southern France. In these countries 

 and in Britain the till bears an identical character. It is not 

 more variable throughout Europe than the author has found it 

 to be in Scotland and Northern England. On the basement- 

 gneiss at Christiansund, in South- Western Norway, it is the 

 fame as on the basement-gneiss of Sutherlandshire ; in the 

 great limestone valley of Eaux Chauds, in the Pyrenees, it is 

 scarcely to be distinguished from the till of the limestone valleys 

 of Yorkshire. In all the places mentioned (more doubtfully 

 at Berlin and Leipzig) it bears the unmistakable character 

 of a ground-moraine accreted under the direct weight of 

 glacier-ice ; its essential character is that of a rude pavement 

 of glaciated debris ground from the rocks over which the 

 glaciers have passed, with its larger boulders firmly glaciated 

 in situ on their upper sides in the direction of ice-movement, 

 and with a tendency to the production of fluxion structure here 

 and there in the matrix, due to the onward drag of the super- 

 incumbent ice. In mere indiscriminateness of composition (which 

 is a character much emphasized by glacialists) the till is not to 

 be distinguished from boulder-clays formed under berg- or raft- 

 ice, such as the highest marine clays of the Norwegian coasts, 

 which are stuck promiscuously through with boulders derived 

 from the glaciers of the interior. The glaciation of boulders 

 in situ the author finds to be a crucial distinction ; he readily 

 detected this ^^striated-pavement'" character in the tills of all the 

 districts above mentioned except Leipzig and Berlin, where the 

 boulder clays more resemble the upper boulder-clay (Hessle clay) 

 of the eastern seaboard of England and Scotland, and in the 

 sections examined by him contained no large blocks. 



Note on a few of the many Remarkable Boulder-stones to 

 he found along the Eastern Margin of the Wicklow Moun- 

 tains, by Prof. Edward Hull, F.R. S. — Amongst the evi- 

 dences of the former existence of an extensive sheet of 

 ice descending from the Wicklow Mountains towards the 

 shores of the Irish Sea is the occurrence of boulder-stones, 

 chiefly formed of granite or granitoid gneiss, derived from the 

 mountainous range to the westward, of a size seldom equalled — 

 probably not surpassed — amongst the British Isles. (i) The 

 Mottha Stone is perched on the summit of Cronhane Hill, above 

 Castle Howard, and is a conspicuous object for all directions- 

 It consists of grey granite, and rests upon Lower Silurian slate ; 

 its weight would be about seventy tons. It lies at a level of 

 816 feet above the sea, and is about 10 or 12 miles from the 

 flanks of Lugnaquilla, whence, as we may suppose, the granite 

 block started on its journey. (2) In the valley between Castle 

 Kevin and Moneystown, where large boulders are numerous, 

 there lies a block of granite about 100 tons in weight. The 

 birth-place of this boulder was probably the mountainous district 

 about Mullaghcleevann, 2783 feet in height, lying at the head 

 of the valley in which is situated the deep waters of Lough Dan, 

 and it probably travelled a distance of 8 or 9 miles in an eat- 

 south-east direction. {3) The last boulder-stone is perhaps the 

 largest in the British Islands. It stands behiiid a cottage by 

 the roadside, near Roundwood Church, and is quite as large as 

 the cottage itself, to which it forms a good protection from the 

 .■-torms descending from the mountains behind. This boulder 

 consists of granitoid gneiss, resting on Lower Silurian slate and 

 grit, and is about 240 tons in weight. The source of this block, 

 which lies at an elevation of about 800 feet above the sea, was 

 probably in the same locality with that of the Castle Kevin 

 boulder, and the distance travelled was about 6 or 7 miles. 

 The blocks above noticed, with many others of smaller size, do 

 not belong to any of the local glaciers which once filled the 

 valleys towards the close of the Glacial epoch, and which have 

 left numerous well-formed moraines in nearly all the principal 

 valleys descending from the Wicklow range. They are to be 

 referred, in all probability, to the earlier stage of intense glacia- 

 tion, in which the whole district was covered with perennial 

 snows and ice, moving eastward into the hollow now occupied 

 by the waters of the Irish Sea. 



On Ne7u Facts 7-elating to Eozoon Canadense, by Sir J. 

 William Dawson, F.R. S. — For several years no new facts re- 

 specting the Canadian Eozoon have been published, though 

 there has been some discussion on the subject abroad. In so 

 far as the author is concerned, this has arisen from the circum- 

 stance that the late Dr. Carpenter had in preparation an 

 exhaustive memoir, for which Canadian material was being sup- 

 plied, but which was unfortunately left unfinished at his death. 

 The material collected for this has now been placed at the 



disposal of Prof. T. Rupert Jones, F.R.S., and in the meantime 

 the pre- ent note is intended merely to direct attention to some 

 new facts recently obtained. The form of Eozoon has been 

 definitely ascertained to be normally inverted conical or broadly 

 turbinate, except where several specimens have become con- 

 fluent, or when rounded masses have been based on some foreign 

 body. The larger specimens are traversed by cylindrical or long 

 conical vertical openings (pores or oscula), around which the 

 laminae, becoming confluent, form an imperfect wall. Some 

 other points of detail were mentioned, and facts were referred 

 to indicating the continuity and definitely stratified character of 

 the beds in the Middle and Upper Laurentian of Canada. A 

 variety of laminated rocks and minerals which had been mis- 

 taken for Eozoon were referred to. Their description in more 

 detail will be found in forthcoming memoirs of the Peter 

 Redpath Museum. 



Elements of Primary Geology, by T. Sterry Hunt, F. R. S. — The 

 author, after recalling his classification of original or non-clastic 

 rocks into Indigenous, Endogenous, and Exotic masses, based 

 on their geognostic relations, gives in a concise form his theory 

 of the genesis of these various groups of rocks, as taught more at 

 length in his recent volume entitled " Mineral Physiology and 

 Physiography." The superficial portion of a cooling globe, con- 

 solidating from the centre from a condition of igneous fusion, 

 he conceives to have been the protoplasmic mineral matter, 

 which, as transformed by the agencies of air, water, and internal 

 heat, presents a history of mineralogical evolution as regular, as 

 constant, and as definite in its results as that seen in the organic 

 kingdoms. This great transformation involves a series of pro- 

 cesses, which include : (l) the removal from the protoplasmic 

 mass, through permeating waters, heated from beneath, of the 

 chief elements of the great groups of indigenous crystalline and 

 colloidal rocks, by what he has called the crenitic process ; (2) 

 the modification of the residual portion by this lixiviation, which 

 rernoves sihca, alumina, and potash, and, by the intervention of 

 saline waters, brings in additional portions of lime, magnesia, 

 and soda ; (3) the partial differentiation, by crystallization and 

 eliquation, of portions of this more or less modified residue, giving 

 rise to the various types of plutonic rocks. The direct and in- 

 direct results of subaerial decay through atmospheric agencies, and 

 those of the products of organic life, are also considered. From 

 the operation of all these processes result progresssive changes 

 in the composition alike of plutonic and of indigenous rocks. 

 The endogenous rocks or veinstones are, like the last, of 

 crenitic origin, and may be granitic, quartzose, or calcareous in 

 their characters. 



The author next considers the conditions of softening and dis- 

 placement of indigenous rocks which permit them to assume in 

 many cases the relations of exotic rocks, and to become extruded 

 after the manner of lavas, as seen in the case of trachytes and 

 many granite- like rocks. Such masses he designates pseudo- 

 plutonic. With these are often confounded the endogenous 

 granitic veinstones, which were formed under similar chemical 

 conditions to the indigenous granites. Masses alike of indigenous, 

 endogenous, and exotic rocks may also become displaced, not 

 through softening, but by being forced while in a rigid state, 

 through movements in the earth's crust, among masses softer and 

 more yielding than they. 



The author also considers the fluxional structure seen in 

 plutonic and pseudoplutonic eruptive masses, which has led some 

 theorists to regard these as of aqueous origin, and others to main- 

 tain that the crenitic stratiform masses themselves are of plutonic 

 origin — two opposite errors which vitiate much of our geologica' 

 literature. The crenitic process, by removing (from beneath wha 

 was the original surface of deposition) the vast amount of materia 

 which forms alike the indigenous, the endogenous, and thd 

 pseudoplutonic rocks, has eff'ected a great diminution in volum^ 

 in the protoplasmic mass, besides that due in later times to exj 

 trusion of plutonic matter itself This decrease in bulk of tha 

 underlying stratum was a potent agent in producing the universa 

 corrugation of the earlier crenitic rocks, and the frequent dis- 

 cordances observed among them. 



The author considei-s further the gradual diminution of thi 

 crenitic process seen in the later periods of Archaean time, and itsl 

 feebler manifestations in Palaeozoic and more recent ages down tol 

 the present. He notes moreover, that, as the result of geographical | 

 changes, erosion and partial deposition alike disturbed the suc-| 

 cession of the later groups of crenitic rocks, none of which can 

 claim that universality and uniformity which belong to the oldest 

 known group, the fundamental granitoid gneiss. 



