IMPORTANCE OF PALEONTOLOGY. 127 



indicate, and a more detailed account might have "been 

 given of the chemical theories of petrifaction ; but enough 

 has been mentioned to convey to the reader a fair idea of 

 what fossils really are,* how they are formed, and how in- 

 dispensable their study is to the right interpretation of the 

 history of our planet. With this preliminary knowledge he 

 will peruse with greater zest and intelligence the Sketches 

 that follow ; and be better able to trace through the ascend- 

 ing stages of time that plan of vital development, the eluci- 

 dation of which has conferred on modern geology its high- 

 est interest and most enduring attraction. 



NOT is it Geology alone that has benefited by the dis- 

 coveries of the palaeontologist. Botany and Zoology have 

 also acquired new interest, and the whole study of Life 

 assumed a broader and more philosophical bearing. Re- 

 stricted to existing forms, the biologist was often perplexed 

 by anomalies he could not solve, and for want of connec- 

 tions he could not trace ; but now that Palaeontology has 

 revealed its myriad forms, and exhibited a Scheme of Life 

 ever ramifying, yet ever interblending in its remotest rami- 

 fications, a clearer and steadier light has been thrown across 

 the path of his investigations. Even to the ordinary ob- 

 server of nature, how much more exalted the conceptions 

 of life which the science of palaeontology imparts ! How 



* Fossils are sometimes arranged into the following classes -.First, 

 the actual substance ; secondly, the substance replaced by other sub- 

 stances ; thirdly, the cast or mould of the substance and this may be 

 either of the hard or of the soft substance ; and, fourthly, those fossils 

 which are now generally called physiological impressions, such as foot- 

 prints, being certain evidence of the animal having been there. Under 

 whatever class they may be arranged, their preservation will depend 

 partly on their own composition, partly on the nature of the stratum in 

 which they are imbedded, and partly on the chemical changes to which 

 that stratum may have been subsequently subjected. The investigation 

 of these particulars, however, belongs more to the professed palaeonto- 

 logist than to the readers of general geology. 



