BRITISH ASSOCIATION. 



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stone occurred a fine sandstone ; the identity of its fossils 

 was doubtful ; it were unsafe to call them Silurian ; the 

 Spirifer represented was evidently one of that peculiar 

 Producta-like group, with tranverse bars, belonging to the 

 carboniferous limestone, and the other fossils seemed to 

 indicate an intermediate term of life. In the lower lime- 

 stone, a Pleurorhynchus was found — a genus which occurred 

 in Devonian, but not in the Silurian rocks; Pentremites 

 were also figured as belonging to this deposit. The lowest 

 deposits, forming the basis of the series contained the usual 

 Silurian forms, Orthidee and Spirifera. These rocks appeared 

 as one series of calcareous deposits, formed under circum- 

 stances less subject to fluctuation than their equivalents 

 in Europe ; and the continuity of specific forms and types 

 of organization seemed to have been much greater than in 

 countries where phj^sical changes produced well defined lines 

 of separation in the deposits. The successive periods of 

 deposition of strata were much better determined by organic 

 forms than by the mineral constitution of the rocks, but in 

 applying this principle, it is impossible to be too cautious, 

 the evidence being not of time, but of circumstance ; the 

 character of the organic remains being determined by the 

 physical conditions of the period. The order of physical 

 changes, and the series of organic life, must be inquired 

 into separately, and their results combined, before we could 

 be safe ; he had no intention of interfering with or under- 

 valuing investigations based on other grounds, but he 

 believed he had presented a view which did not clash in its 

 result with that given by investigations of another kind. 



Mr. Sedgwick contended, that the expression law was not used in 

 a correct sense, if, by using it, we excluded the idea of laws of a higher 

 order : it merely implied that, having grouped together a set of pheno- 

 mena, we used the term to represent the state of our knowledge at any 

 moment of time. Such were the laws of the distribution of organic 



