644 HISTORY OF GEOLOGY. 



out dwelling on other observations of like kind, I 

 may state that Mr. Lyell has treated this subject, 

 and all the topics connected with it, in a very full 

 and satisfactory manner. He has explained 13 , by 

 an excellent collection of illustrative facts, how de- 

 posits of various substance and contents are formed; 

 how plants and animals become fossil in peat, in 

 blown sand, in volcanic matter, in alluvial soil, in 

 caves, and in the beds of lakes and seas. This 

 exposition is of the most instructive character, as a 

 means of obtaining right conclusions concerning the 

 causes of geological phenomena. Indeed, in many 

 cases, the similarity of past effects with operations 

 now going on, is so complete, that they may be 

 considered as identical ; and the discussion of such 

 cases belongs, at the same time, to Geological Dyna- 

 mics and to Physical Geology ; just as the problem 

 of the fall of meteorolites may be considered as 

 belonging alike to mechanics and to physical astro- 

 nomy. The growth of modern peat -mosses, for 

 example, fully explains the formation of the most 

 ancient : objects are buried in the same manner in 

 the ejections of active and of extinct volcanoes; 

 within the limits of history, many estuaries have 

 been filled up ; and in the deposits which have 

 occupied these places, are strata containing shells 14 , 

 as in the older formations. 



13 B. iii. c. xiii. xiv. xv. xvi. xvii. 



14 Lyell, B. iii. c. xvii, p. 286. See also his Address to the 

 Geological Society in 1837, for an account of the Researches of 

 Mr. Stokes and of Professor Goppert, on the lapidification of 

 vegetables. 



