Section of Geology and Geography. 485 



Professor Sedgwick explained the mode of connecting Mr. Mur- 

 chison's researches with his own, so as to form one general system. 

 He pointed out also the limit, as at present known, of fossils, none 

 having been hitherto discovered in the Lower Cambrian schists, and 

 remarked in reviewing the general phenomena, that geological epochs 

 were not effected by shocks, but, like everything in nature, were 

 under the dominion of the usual laws of causation. 



Notices of the Geology of Spain. By Dr. Traill. 



The author gave a sketch of the results of his personal researches 

 in the geology of Spain, restricting himself, however, to a few only 

 of the more striking peculiarities. He stated that it was an error to 

 suppose all the mountain chains of Spain branches of the Pyrenees, 

 from which they are in many cases completely separated. The va- 

 riety of climate, and circumstances produced by the union of these 

 mountains with the elevated table lands of New Castile, which is two 

 thousand feet, and of Arragon, which is two thousand five hundred 

 feet above the sea, had very peculiar eifects on the flora of the coun- 

 try. Dr. Traill pointed out the identity of character which existed be- 

 tween the granites and schists of Spain and England, and proceeded 

 to the newer strata ; described the brine springs and salt lakes of 

 Andalusia, and the deposit of salt which forms part of the base of 

 the plain of Grenada. He also showed that lias and true chalk, with 

 layers of flint, occur in the South of Spain, and confirmed the state- 

 ments by Colonel Silvertop, of the tertiary deposits of Spain. Dr. 

 Traill further observed, that bones are found in the fissures of other 

 hills in Spain besides that of Gibraltar. 



On certain Disturbances in the Coal Strata of Yorkshire having a 

 remarkable Relation to existing Valleys ; illustrated by a Map and 

 Sections. By Henry Hartop. 



M. Agassiz presented the fourth and fifth livraisons of his 

 work on Fossil Fishes, and stated, that by the great addition of 300 

 species which had been obtained from the cabinets of these countries, 

 the total number had been raised to about 900. He then advanced 

 some general views on the conclusions to be drawn from the geolo- 

 gical distribution of fishes, and explained the precision in determining 

 epochs which their higher state of organization and consequent 

 susceptibility to external influences afforded. The fishes of the car- 

 boniferous period were different from those of the lias ; the fishes of 

 the lias different from those of the oolite ; and those of the oolite 

 from the fishes of the chalk : and as it must be presumed that fishes 

 living together so coexist from the necessity of their organization, 

 and its adaptation to attendant circumstances, it must also be pre- 

 sumed that their disappearance was the result of a change in the 

 conditions of the earth's surface. In estimating the effects of such 

 changes, it is necessary, M. Agassiz observed, to distinguish between 

 generaf phenomena affecting, as it were, the laws of nature, and 



