517 



tomical investigation of the infusoria, and has discovered that 

 their internal structure is often very complicated, that they have a 

 distinct muscular and nervous system, intestines, sexual organs 

 of reproduction, and that some of them are provided with sili- 

 ceous shells, or cases of pure silex. The forms of these dura- 

 ble sliells are very marked and various, but constant in particular 

 genera and species. They are almost inconceivably minute, yet 

 they can be clearly discerned by the aid of a powerful microscope, 

 and the fossil species preserved in tripoli are seen to exhibit in the 

 family Bacillaria and some others the same divisions and transverse 

 lines which characterize the shells of living infusoria. 



In the Bohemian schist of Bilin, and in that of Planitz in Saxony, 

 both of them tertiary deposits, the species are freshwater, and are 

 all extinct. The tripoli of Cassel appears to be more modern, and 

 the infusoria in that place, which are also freshwater, are some of 

 them distinctly identical with living species, and others not. In the 

 tripoli brought from the Isle of France, the cases or shells all be- 

 long to well-known recent marine species. 



The flinty shells of which we are speaking although hard are 

 very fragile, breaking like glass, are therefore admirably adapted 

 when rubbed for wearing down into a fine powder fit for polish- 

 ing the surface of metals. It is difficult to convey an idea of 

 their extreme minuteness, but I may state that Ehrenberg esti- 

 mates that in the Bilin tripoli there are 41,000 millions of indivi- 

 duals of the Gaillonella distans in every cubic inch of stone. At 

 every stroke therefore of the polishing stone we crush to pieces se- 

 veral thousands if not myriads of perfect fossils. 



Gentlemen, — Although I have already extended this Address be- 

 yond the usual limits, I cannot conclude without congratulating you 

 on the appearance of Dr. Buckland's Bridgewater Treatise, a work 

 in the execution of which the author has most skilfully combined 

 several distinct objects. He has briefly explained the manner in 

 which the materials of the earth's crust are arranged, and the evi- 

 dence which that arrangement affords of contrivance, wisdom, and 

 foresight, He has also given us a general view of the principal facts 

 brought to light by the study of organic remains; thus contributing 

 towards the filling up one of the greatest blanks which existed in 

 the literature of our science, while at the same time he has pointed 

 out the bearing of these phasnomena on natural theology. 



