Outlines of Geology. ■ 247 



expect from the perusal of certain systematic geological writers, 

 are not in general to be met with in nature. 



Another circumstance by which some of the rocks we have 

 just considered are distinguished from others, and more especially 

 from those formerly described, is the defalcation of organic relics 

 both in quantity and perfection. The shells and corals, so abun- 

 dant in the mountain limestone, are not blended with any kind of 

 bones, nor are there are any vegetable remains ; and in the under* 

 lying sandy and schistose formations a solitary shell now and 

 then occurs, whilst in the micaceous slates, and the rocks belong- 

 ing to the granitic family, which next claims attention, and will 

 form the subject of the next lecture, there is neither shell nor 

 coral, nor any impression or semblance of any thing that has ever 

 appertained to the organized kingdoms of nature. The gradual 

 transitions of one kind of rock into others on the one hand, and 

 their sudden and abrupt lines of demarcation on the other ; their 

 verticality in one place, and their horizontality in others j their 

 occasional resemblances, and frequent dissimilarities, are a few of 

 the circumstances which will lead the cautious and unprejudiced 

 observer to distrust those accumulations of hypotheses which have 

 sometimes been dignified by the title of geological theories, but 

 which, in assigning opposite virtues to the same subject, are alike 

 at variance with nature and with themselves — they are systems 

 which might pass for the inventions of those ages a when sound 

 philosophy had not as yet alighted on the earth, nor taught man 

 that he is but the humble minister and interpreter of nature." 



VII. 



We have now cleared our way to the primitive formations of 

 the Wernerians, and have arrived at those strata, or rocks, upon 

 which all others appear to rest, and which, towering up through 

 the superincumbent substances, form the exposed peaks and 

 loftiest summits of the principal mountain-chains of the world. 

 Whether these rocks are to be regarded as original formations* 



