46 Proceedings of the Royal Physical Society. 



" Cedarville Limestone," or " Pentamerus Limestone." Dolo- 

 mites of the same age, and containing the same fossils, have 

 also been described as occurring at Leclaire in Iowa, at Port 

 Byron and near Chicago in Illinois, and at Eacine in Wis- 

 consin. 



The remainder of the paper was occupied with a general 

 account of the organic remains of the Guelph limestones. 

 Fossils are numerous in the beds of this formation, but are 

 poorly preserved, and are for the most part in the form of 

 casts. The most highly characteristic forms are the Trimerel- 

 lidoe and Pentameri amongst the Brachiopoda, the Megalomi 

 amongst the Lamellihranchiata, and the numerous species of 

 Murchisonia, Pleurotomaria, and Holopea amongst the Gastero- 

 poda. Upon the whole, it may be concluded that the Guelph 

 dolomites constitute a distinct series of deposits, which, how- 

 ever, clearly are to be regarded as merely a subordinate stage 

 in the great Niagara Formation. 



II. — Suspension of Clay in Water. By William Durham, Esq., 



F.E.S.E. 



On January 28, 1874, I read a paper on this subject before 

 this Society. This paper was afterwards published in the 

 Chemical News of August 7, vol. xxx., No. 767. The following 

 were the results then noted : 



(1.) The clay rapidly separated into two portions ; the 

 greater part quickly settling down to the bottom of the jars, 

 the lesser part remaining suspended in the liquid consider- 

 ably longer. 



(2.) The power which water possesses of sustaining clay 

 is gradually destroyed by the addition of an acid or salt. 



(3.) In solutions of sulphuric acid and sodium chloride, of 

 varying strengths, the greater part of the clay sunk to the 

 bottom of the jar, and the liquid became clear in the order of the 

 specific gravities of the solution, so that the densest liquid settled 

 and cleared last. This effect was more decided in the acid 

 than in the salt solutions. 



(4.) In solutions of sodium carbonate of varying strengths 



