NA TURE 



[September 28, 189; 



in which minerals were segregated into bands, often parallel, and 

 containing one prominent mineral in large crystals. Pegmatite 

 veins, traversing not only massive unfoliated rocks, but the 

 segregated bands, also occurred. These structures were best 

 seen in ancient plutonic masses, but had also been lately 

 observed by the author in the recent volcanic rocks of the 

 Western Isles of Scotland. 



On "Berthelot's Principle applied to Magmatic Concentra- 

 tion," by A. Harker. The paper deals with that type of con- 

 centration in which an igneous rock-magma, supposed originally 

 homogeneous, has been differentiated by accumulation of the 

 more basic ingredients in the cooler marginal part of the liquid. 

 The author tries to find a physical cause for this action by com- 

 paring such a magma with a saturated %^vas. solution, and apply- 

 ing Berthelot's "principle of maximum work " or the cognate 

 one of "most rapid degradation." The migration of the least 

 soluble ingredients to the part of the liquid most easily saturated 

 would determine crystallisation, the process which in the case 

 supposed would give the most rapid evolution of heat. 



On "The Igneous Rocks of Barnavave, Carlingford," by 

 Prof. W. J. Sollas. The white granophyre of this tract is 

 intrusive into a black gabbro, in dykes of all sizes down to the 

 most minute films and specks amongst the constituents of the 

 latter rock. The result of this intimate intrusion is to convert 

 the gabbro locally into a quartz gabbro, whilst the granophyre 

 is loaded with fragments varying from large masses to crystal 

 dust derived from the fracture of the gabbro, thus becoming a 

 hornblendic granophyre. These intermediate rocks have been 

 made out of a mixture of acid and basic constituents. The same 

 author gave an analysis and microscopical description of an intru- 

 sion of Amphibolite at Glendalough, which, at its margin, had 

 been transformed into Quartz-mica-diorite by the action of veins 

 which were filled with potash felspar in the hornblende rock, 

 but with quartz in the adjacent schists. Both these papers were 

 well illustrated by lantern slides. Prof. Sollas also exhibited 

 some pebbles from an ancient consolidated beach at Sandy- 

 mount, CO. Dublin, which had impressed one another on account 

 of the perpetual jarring of the tram-cars running over them. He 

 thought it was likely that earth tremors had had considerable 

 influence in producing the similar pittings in Triassic pebbles. 

 Bearing on this subject Dr. V. Ball showed incised bones and 

 antlers from Irish peat-bogs, the cuts on which were due to 

 pressure and tremors passing through the bog. 



There were two papers, by Mr. W. W. Watts, on Irish 

 petrology ; one, "On a Hornblende-Pikrite intrusive in Cam- 

 brian Rocks at Greystones, co. Wicklow," described a rock 

 consisting mainly of green and colourless hornblende enclosing 

 grains of olivine, now converted into a mineral-like colourless 

 amphibole ; and another, "On the Perlitic Qaartz Grains in 

 Khyolite of Sandy Braes Quarry in Antrim," in which the 

 porphyritic quarlz grains exhibited a series of concentric cracks, 

 perlitic in character, the bulk of which were confined to the 

 quartz crystals, but some of which traversed quartz and matrix 

 alike. 



" On Augen-Structure in Relation to the Origin of Eruptive 

 Rocks and Gneiss," by Mr. J. G. Goodchild. Passing over 

 that type of this structure more properly named phacoidal, the 

 author confined himself to those "eyes" of minerals which 

 have grown in sitn in the rock where they occur. In cases 

 where the original rock contained the necessary material for 

 the formation of the " eyes," a rise in temperature or relief in 

 pressure sufficient to enable the less refractory minerals to 

 aggregate, but not sufficient to alter the chemical and physical 

 state of the matrix, appears to have been all that is necessary. 

 In other cases the author suggested that the necessary alkalies for 

 the formation of such substances as secondary felspars may 

 have been derived from the inner zones of the earth's crust. 



A very useful and well-illustrated paper was read by Mr. 

 Arnold-Bemrose, " On the Derbyshire Toadstone." Thereare 

 two, at least, and may even be three or four, beds of olivine 

 dolerite associated with tuffs. The rock is columnar and 

 spheroidal, and may frequently be met with in an undecom- 

 posed state when the augile occurs in grains or ophitic plates 

 containing felspar or olivme. There appears to be no foundation 

 for the supposition that the toadstone contains no lead ore. All 

 these rocks are surface lava flows. 



Messrs. Howard and Small divide the igneous rocks of South 

 Pembrokeshire into a northern group of rhyolites associated 

 with quartz diorites and granites, often gneissose in character, 

 and with epidiorites and hornblende schists, and a southern 



NO. 1248, VOL. 48] 



group at Musclewick Bay, consisting of porphyrites and 

 dolerites in connection with a rock like a soda felsite. The 

 authors are unable to fix the age of the rocks, but think the 

 evidence goes to show that the rocks are, at the earliest, of 

 Post-Silurian date. 



Amongst the local papers, one by Prof. Clowes was of con- 

 siderable interest. In it he showed the rock of which Bramcole 

 and Stapleford hills and the Himlack stone were composed, 

 was cemented by barium sulphate present occasionally in such 

 quantity as to make 50 per cent, of the whole rock. Sometimes 

 the crystalline cement was evenly distributed in minute crystals, 

 but at others it was aggregated into patches which made the 

 rock weather unevenly, so as to produce the so-called " pebble 

 sand-beds." The author had no evidence of the form in which 

 the cement was originally deposited — whether as carbonate or 

 directly as sulphate. 



Prof. E. Hull pointed out that the Nottingham water supply 

 was derived from the Bunter sandstone, which was underlaid by 

 the impervious Permian marls. Allowing that 20 out of 30 

 inches percolated into the sandstone, he calculated that the 

 area of its outcrop from Worksop to Nottingham (120 square 

 miles) must receive 40,000,000 gallons, all of which tends to 

 flow eastwards. From the three stations about S\ million 

 gallons were pumped daily. In a note on " The Borings at 

 Netherseal Colliery," Prof. Hull determines the lowest rocks 

 reached under Trias and Coal Measures at a depth of abcut 770 

 feet from the surface, as grits, sandstones, and quartzite, and 

 attributes to them a Lower Cambrian age. 



A number of more or less local papers relating to the new 

 red sandstones were grouped together. Prof. Lapworlh gave a 

 general account of the subdivisions, distribution, and thickness 

 of these rocks in the Midlands. Mr. Irving followed with ^risumt 

 of his researches for twenty years into the younger red rocks, refer- 

 ring to the classing of the Devonshire igneous and lower stratified 

 red rocks as Permian in the recently published index maps of the 

 Geological Survey. Mr. Metcalfe gave a note on the Gypsum 

 deposits of Notts and Derbyshire. Baron von Reinach and 

 Mr. Ussher recorded the discovery of Upper Magnesian lime- 

 stone shells at Bulwell, and Messrs. Kendall and Gray showed 

 that the presence of Permian marls at Stockport destroys the 

 supposed evidence of unconformity there between the Permian 

 and Trias. 



After a brief discussion on Geological Education, Tuesday was 

 devoted to glacial papers and discussion. Mr. Dugalc^ Bell 

 read an abstract of a most careful and important investigation 

 into the shell -bearing clays of Clava in Nairn. The section in 

 descending order, proved by excavation and boring, is as 

 follows : — 



(1) Surface soil and sandy boulder clay ... 



(2) Fine sand 



(3) Shelly blue clay with stones in lower part 



(4) Coarse gravel and sand 



(5) Brown clay and stones ... 



(6) Solid rock. Old Red grit 



Feet. 



43 

 20 

 16 

 15 



2'4 



The highest part of the shelly clay is 5031 feet above sea level, 

 and the deposit appears to be continuous for a distance of 190 

 yards. It contains far-travelled, well-rounded stones (one 

 must have come at least twelve miles) associated in different 

 proportions from those in the overlying boulder clay or under 

 lying gravel. The shells are mainly littoral, though some- 

 may have lived at depths not greater than twenty fathoms j 

 although not intensely arctic, they indicate a colder climate than 

 the present. The shells are well preserved, neither rubbed nor 

 striated, and the deposit is a true marine silt, which if not in 

 situ must have been transported in mass. The direction of ice 

 flow being from south, or a little west of south, shows that the 

 ice did not pass over any existing sea-bed before reaching Clava, 

 and if the clay was carried from Loch Ness a submergence is 

 postulated by the marine fauna there. The majority of the com- 

 mittee consider the evidence sufficently strong to prove a sub- 

 mergence to the extent of 500 feet, and they think the passage of 

 ice to form the upper boulder clay would be sufficient to cause 

 the cracking of the shelly clay and the crushing of certain of the 

 shells. Detailed reports and lists of organisms are given, and a 

 " minority report" on the evidence bearing against the view put 

 forward above. Mr. Bell, in a paper, commented on shelly clay 

 and gravel extending along the east coast of Aberdeenshire from 

 the sea level up to about 300 feet, and endeavoured to explain it 



