74? Geological Society -.Royal Institution. 



west only a few degrees, and the inclination approaches the vertical 

 with a strike N. and S., or nearly perpendicular to that of Exmoor. 



What, says Mr. Williams, are the results, if the question be tested 

 by the assumed law, that strata may be identified by their organic 

 remains ? If the Posidonise and Goniatites of the lenticular, black 

 limestones, never exceeding thirty-five feet in thickness, be appealed 

 to, to identify them with the mountain limestone, the weight of 

 organic remains opposed to them in the Launceston and Petherwen 

 fossils, the corals and other organic remains of South Devon belong- 

 ing to the ftoriferous series, reduces the evidence to dust. If mineral 

 characters be appealed to, he says, they fail altogether. 



In conclusion, Mr. Williams remarks, that in this supplement, he 

 has endeavoured faithfully to transfer the simple truths of nature to 

 his pages, without reference to the theories of others. He would, 

 however, remind geologists that the proposed law of Mr. W. Smith 

 is no law, if it do not imply a final and universal extinction of 

 species. This being his own view, Mr. Williams says, he could not 

 admit that the Goniatites and Posidoniae of Devonshire were first 

 introduced and became extinct with the mountain limestone, being 

 justified by the fact of superposition, and more reasonable analogy, 

 in concluding that these genera existed elsewhere in congenial con- 

 ditions during the entire period of the deposition of the Trilobite 

 slates, when that formation ceasing in Devonshire, the ova of the 

 creatures or the creatures themselves were transported to a region 

 favourable to their existence, and were continued during epochs of 

 duration up to the period of the mountain limestone, and probably 

 beyond it, if they be not now in existence. They appear, in his 

 opinion, like the corals of Devon, to have been subject to repeated 

 mineral accidents, and to have been locally destroyed in groups, 

 not universally effaced in species. To guard himself, however, from 

 misconstruction, Mr. Williams adds, he believes entirely in the ex- 

 tinction of genera and species ; but at very distinct epochs, and in 

 far thicker and more extended groups of strata than is imagined ; 

 and that consequently the identification of strata must be regulated 

 by a per-centage test similar to that applied by Mr. Lyell to the 

 tertiary series. Lastly, he protests against the determination of 

 the age of the Devonshire formations by reference to the structure 

 of a foreign district. 



PROCEEDINGS AT THE FRIDAY-EVENING MEETINGS OF THE 

 ROYAL INSTITUTION. 



May 1. Mr. Griffiths on the sources and uses of sulphuric acid. 

 May 8. Mr. Faraday on the origin of electricity in the Voltaic pile. 

 May 15. Mr. Macilwain on respiration and its relation to ani- 

 mal temperature. 



May 22. Mr. Brande on white lead. 



May 29. Mr. Brockedon on some new applications of caoutchouc. 



June 5. Rev. Dr. Scoresby on magnetism. 



June 12. Mr. Carpmael on the manufacture of wire cards. 



