March 30, 1876] 



NATURE 



439 



SOCIETIES AND ACADEMIES 

 London 

 Geological Society, March 8. — Pro. P. Martin Duncan, 

 F.R.S., president, in the chair. — W. J. Chetwood Crawley, Walter 

 Keeping, Joseph Thompson, and William Walker, were elected 

 Fellows of the Society. The following communications were 

 read : — i. On the influence of various substances in accelerating 

 theprecipitationofclay suspended in water, by Mr. Wm. Ramsay 

 Principal Assistant in Glasgow University Laboratory. Com- 

 municated by Prof. Ramsay, F.R.S., V.P.G.S. The author 

 referring to the fact that clay when suspended in water in 

 excessively minute particles, settles more rapidly when the water 

 contains salts in solution, noticed the opinions expressed by pre- 

 vious writers on the subject, and gave the results of experiments 

 made by him, from which it would appear that the rapidity of 

 precipitation is proportionate to the amount of heat absorbed by 

 the salts in process of solution. By another series of experiments 

 he found that the fluidity of the respective solutions had apparently 

 no influence on the rapidity of deposition of the clay. He also 

 found that clay is deposited less quickly in acid solutions than in 

 solutions of salts, and more rapidly in a solution of caustic soda 

 than in one of caustic potash. In solutions of common salt of 

 different strengths he found that clay settled in the inverse order 

 of their speci^fic gravities. From all these results the author is 

 inclined to attribute the varying rapidity of the settling of clay 

 suspended in saline solutions to the varying absorption of heat 

 by the solutions. When water containing suspended clay was 

 heated, the rapidity of the settling of the clay was proportionate 

 to the heat of the water. The author suggests that the increased 

 rapidity of settlement may be due to the greater amplitude of 

 vibration of the molecules of water when heated ; the vibrations 

 being performed in equal times, particles descending at right 

 angles to the plane of vibration will experience less resistance 

 from the molecules of water. A note by Prof. Ramsay, briefly 

 indicating some of the geological bearings of these results, was 

 appended to the paper. — 2. On some Fossiliferous Cambrian 

 Shales near Carnarvon. By Mr. J. E. Marr. Communicated 

 by Prof. T. McKenny Hughes, F.G.S. With an Appendix, by 

 Mr. Henry HicL«. Tl e shales described by the author extend 

 from about three miles S.W. of Carnarvon to Bangor, running 

 nearly parallel to the Menai Straits. They are faulted against 

 Lower Cambrian to the east, and disappear against a dyke on 

 the west. The shales vary from greyish black to bluish black 

 in colour, and are generally sandy and micaceous, but in places 

 chiefly clayey. Fossils were obtained from three places on the 

 banks of the Seiont, namely, near Point Seiont (where the beds 

 are concretionary in structure), along the old tramway from 

 Carnarvon to Wanttle, and near Peblig Bridge. The first-named 

 locality is richest in fossils ; and here there is a greenstone dyke, 

 parallel to the bedding of the rock, and altering the shales for a 

 distance of about four yards from the edge of the dyke. The 

 fossils seem to indicate that the deposit belongs to the upper 

 part of the Arenig group. Mr. Hicks pointed out that the fauna 

 clearly showed that these beds belong to the Arieng group, many 

 of the species being identical with those found in the upper part 

 of that group at St. David's Shelve, and in Cumberland. The 

 new species found by Mr. Marr are a Caryocaris {C. Marrii) 

 and an ALglina {A. Hii^hesii). The other fossils were Didymo- 

 graptus indentus, D. bifidus, D. Murchisani, and the var. furcil- 

 latus. Species of Barrandea, TrinucUus, Lin^tla, Obolella, 

 Discina, ik.c. , and Orthoceras caeresiense. The rock in its general 

 character is extremely like that at the same horizon in the 

 succession at St. David's Shelve, and in Cumberland, and indi- 

 cates, therefore, the prevalence of similar physical conditions 

 when deposited. The rock is such as would be formed over an 

 even sea-bottom at some considerable distance from land and in 

 moderate deep water. Mr. Hicks looked upon this discovery as 

 of considerable importance, since it clearly proved the position 

 of beds hitherto imperfectly known, and moreover shows that 

 similar conditions prevailed over extensive areas at the time these 

 beds were deposited. It also furnished further evidence in support 

 of Mr. Hicks 's opinion that no break occurs anywhere in the 

 Welsh area between the Cambrian and Lower Silurian rocks. 

 ' — 3. On the occurrence of the Rhartic Beds near Leicester. By 

 Mr. W. J. Harrison, Curator of the Town Museum, Leicester, 

 The sections described by the author are shown in brick-pits in 

 the Spinney Hills, forming the eaitern boundary of the town of 

 Leicester, and in the Crown Hill on the eastern side of a valley 

 excavated by the Willow Brook. In the latter locality they are 

 capped by Lower Lias. They have a slight dip to the south-east. 



The brick-pits show a thickness of about 30 feet of Rhjetic beds 

 above the Triassic red marl, to which their stratification is 

 parallel. The lowest bed is a light-coloured sandy marl about 

 1 7 feet thick, traversed by three or four courses of harder, whiter 

 stone, and containing crystals of selenite, pseudomorphs of salt, 

 and numerous small fish-scales. A single insect wing was 

 obtained from it. This bed extends across the valley of the 

 Willow Brook, and forms the base of Crown HilL Above it 

 comes the Bone-bed, from 2 to 3 inches thick, containing 

 numerous small teeth, bones, and scales of fishes and Saurians, 

 including large vertebrje of Ichthyosaurus, ribs probably of 

 Plesiosaurus, and some bones of Labyrinthodont character. Two 

 species of Axinus also occur. The Bone-bed is followed by 

 about 2\ feet of coarse black shales, overlaid by a very thin band 

 of hard reddish sandstone, with casts of Axinus, and this by 

 about 2 feet of finely laminated black shales containing Cardium 

 rhiEticum, Aiicula coutorta, and a Starfish {Ophiolepis Damesii). 

 Above these come about 5 feet of shales \vith sandy partings, the 

 lower foot rather dark and containing Avkula contorta, Cardium 

 rhaticum, Ostrea iiassica, and a new Pholidophorus ; the re- 

 mainder light-coloured, but with the same shells. The topmost 

 bed in the section is a band of nodular limestone 6 inches thick. 

 The same sequence is observed in Crown Hill. There are indi- 

 cations of the existence of a second nodular limestone and of 

 beds of light-coloured clay and sand, but obscured by drift, in 

 which, however, blocks of limestone occur with Monotis decussaia 

 and Afwplophora musculoides. The author indicates other 

 localities where traces of the Rhoetic beds are to be seen, and 

 states that wherever the true junction of the Trias and Lias is 

 exposed, the Rha^tics appear to be invariably present. The paper 

 also included some particulars with regard to borings in the Trias 

 near Leicester. — 4- Hsematite in the Silurians. By Mr. J. D. 

 Kendall. The author referred to a former paper in which he 

 showed that direction of the haematite deposits in the Carboni- 

 ferous Limestone of Cumberland and Lancashire is parallel to 

 that of the meridional divisional planes, or nearly north and 

 south ; while the deposits in the Silurians are in two directions, 

 some parallel to one set of divisional planes and some to the 

 other. In the present paper he describes a leposit of hematite 

 at Water Blean, in the parish of Millom in Cumberland, in 

 Coniston Limestone, which appears to be altogether unlike those 

 referred to in his former paper. The Silurians here are all con- 

 formable, with a stiike about 65° N.E. and S.W. and a dip of 

 about 80° to X. W., but their order is inverted. The haematite 

 occurs in the Coniston Limestone in the form of short veius, 

 varying in width from a few inches to 9 feet, running in the di- 

 rection of the strike, and having the same dip as the limestone, 

 their deposition having taken place along the bed -joints of the 

 rock. The author accounts for this diflference in the deposits by 

 the fact that in the Coniston Limestone at Water Biean the bed- 

 joints are much more persistent than the divisional planes, which 

 are very irregular and not at all so strong and open as the bad- 

 joints. 



Zoological Society, March 21. — Dr. E. Hamilton, vice- 

 president, in the chair. — Mr. Sclater exhibited and made remarks 

 on a series of skins of the parrots of the Fiji Islands, obtained 

 by Mr. E, L. Layard belonging to the collection of Lord Walden, 

 and called special attention to a new species of the genus Pyr- 

 rhulopsis of Reichenbach from the Island of Taviuni, which 

 Mr. Layard had proposed to call P. taviuntnsis. — Mr. A. G_ 

 Butler read a paper containing descriptions of some new 

 Lepidoptera from the collection of Lieut. Howland Roberts. — 

 A communication was read from Mr. Andrew Anderson, con- 

 taining corrections of and additions to a former paper of his on 

 the Raptorial Birds of N orth- Western India. — Mr. Howard 

 Saunders read a paper on the Stercorariiniz or Skua Gulls, in 

 which he revised and corrected the synonymy of several species, 

 and traced their respective ranges so far as they were known. 

 He considered that Stercorarius chilensis (Bp.), although more 

 nearly allied to the Northern form S. catarrhcctes than to S. 

 antarcticus, was perfectly distinguishable from either by its con- 

 stant rufous coloration of the underpaits and axillaries ; its range 

 as at present known being restricted to the West coast of South 

 America. The range of SUrc. pomatorhinus was shown to 

 extend from S. lat. 82^ N. to about 3^ S., and that of 

 Richardson's Skua, to whi;h he restored the original, but lately 

 disused name of Stercorarius crepidatus reached from 82° N. to 

 more than 40° S., on the coast of New Zealand : S. spinicauda 

 (Hardy), from the African coast, being regarded as merely this 

 bird in winter dress. 



