230 Reports and Proceedings — 



We cannot close tins notice without a few words in acknowledg- 

 ment of Mr. Judd's disinterested devotion to Geology; for after 

 resigning liis appointment on the Geological Survey, he gave up his 

 own time to the preparation of this Of&cial Memoir. 



The work of the Survey, rendered more detailed every year by the 

 advance of the science, would seem no light work as fresh districts 

 are entered, and the literature of the subject comes to be studied. 

 And when Mr. Topley tells us that great part of his Memoir was 

 prepared amongst the Northumbrian Moors, we can understand that 

 literary work involving bibliographical research was carried on at 

 considerable disadvantage. To him and to Mr. Judd great credit is 

 due for the admirable manner in which all the facts connected with 

 the respective districts they have described are placed before their 

 readers. We do not think that the task of either could have been 

 performed more satisfactorily, and we can only regret that the price 

 of 28s. is likely to debar many poor geologists from purchasing Mr. 

 Topley's Memoir, while the price of 12s. 6cZ. for Mr. Judd's book 

 seems disproportionately low. The volumes, moreover, neither cor- 

 respond in size nor in the "lettering," but these are mysteries which 

 we cannot pretend to fathom; they are among the hidden things of 

 Her Majesty's Stationery Office, and past finding out ! 



I^:E3:FOI^TS j^jistid :FI^oc:E:B^DII^^C3-S- 



Geologioal Society of London. — I. — March 8, 1876. — Professor 

 P. Martin Duncan, M.B., F.E.S., President, in the Chair. 



The following communications were read : — 



1. " On the Influence of various substances in accelerating the Pre- 

 cipitation of Clay suspended in Water." By Wm. Eamsay, Esq., 

 Principal Assistant in Glasgow University Laboratory. Communi- 

 cated 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 

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

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

 cipitation 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 in- 

 fluence 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 specific 

 ■gravities. From all these results the author is inclined to attribute 

 the varying rapidity of the settling of clay suspended in saline solu- 

 tions 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 



