234 NATURAL 



abundant of these, viz. gravel, sand, clay, loam, marl, 

 ealc-tufT, calc-sinter, brown coal, and peat. 



Petrifactions frequently occur distributed through 

 these deposites either in a regular or irregular manner, 

 and are sometimes whole, sometimes more or less broken, 

 but angular, or are so much rounded as to show that 

 they have suffered by attrition. Several different allu- 

 vial formations may be pointed out, which are charac- 

 terized by the organic remains they contain. Thus, one 

 formation found in this neighbourhood contains shells 

 of the common oyster, common muscle, patella vulgaris, 

 4}ucinura undatum and lapillus, nerita littoralis, and turbo 

 Jittoreus, all of which are still inhabitants of the Frith of 

 Forth. Another contains bones of ruminating animals, 

 as those of the horse, ox, and stag, but differing from 

 those of the living species ; and in a third, which con- 

 tains such marl and many fresh-water shells, there occur 

 the bones of several extinct species of the elephant r rhi- 

 noceros, hippopotamus, and also of the Irish elk, which 

 is no longer a native of this country.* 

 I'V-'wYjWa,,? . ?,. . ^:^<i : .'. <6;>4<T* 



From the preceding short sketch it appears, that the 

 most simple animals are those we first meet with in a 

 mineralized state ; that these are succeeded by others 

 more perfect, and which are contained in newer forma- 

 tions ; and that the most perfect, as quadrupeds, occur 

 only in the newest formations. But we naturally inquire, 

 have no remains of the human species been hitherto dis- 

 covered iw any of the formations ? Judging from the ar- 

 rangement already mentioned, we would naturally ex- 

 pect to meet with remains of man in the newest of the for- 

 mations. In the writings of ancient authors, there are 



* This latter formation has been lately discovered in Ayrshire, 



