105 



Anniiaire de I'Observatoire de Bruxelles pom- I'an 1835. Par le 



Directeur A. Quetelet. — £1/ the Author. 

 A Treatise on Inoectg. By James Wilson, Esq. F. R. S. E. 

 A Treatise on Fishes. By James Wilson, Esq. F. R. S. E Bt/ 



the Author. 

 De rinfluence de la Lune sur I'Atmosphere Terrestre, dotermin^e 



par les Observations Meteorologiques. Par M. Eug. Bouvard. 



— By the Aut/ior. 

 Memorias para a Historia das Navaga^oes e Descobrimentes das 



Portuguezes. Par Joaquim Jose Da Costa De Macedo. — By 



the Author. 

 A Collection of Specimens from the Volcanic District of Auvergne. 



—Collected and presented by Professor Forbes. 



The following Communications were read : — 



1. Notes on the Geology of Auvergne, particularly in con- 

 nection with the Origin of Trap-Rocks and the Eleva- 

 tion Theory. By Professor Forbes. Concluded. 



The first part of this paper (which accompanied a series of geo- 

 logical specimens from Auvergne, presented to the Society) relates 

 to several specific points which tend to assimilate the evidence for 

 the igneous origin of trap-rocks generally, with that afforded by 

 the volcanic district of Central France. The altered character of 

 the stratified deposits with which igneous rocks have been inter- 

 mixed, is one of their most striking features ; yet we occasionally 

 find cases where this evidence is far from being so obvious as 

 might be expected ; and this dubious character, which is particu- 

 larly remarked in the hill of Gergovia, near Clermont, forms an 

 admirable parallel to some cases in trap districts where a like want 

 of alteration occurs. 



The mineral character of the rocks of Auvergne admits of al- 

 most perfect identification in a majority of cases with that of un- 

 doubted trap-rocks ; and we may employ the formations of Central 

 France as a medium of comparison between trap-rocks generally, 

 and modern volcanos, from which the formations of the Monts 

 Dome are undistinguishable. The trachytes of the Mont Dor and 

 Cantal find their counterparts in the districts of the Siebengebirge 

 and Laacher-Lee. Various points of structure were noticed as 

 important, especially the columnar forms of lavas, geologically 



