THE EARTH. 



15 



certainly the first, although the most morti- 

 fying conduct. For my own part, were I to 

 offer a conjecture, (and all that has been said 

 upon this subject is but conjecture,) instead 

 of supposing them to be the remains of ani- 

 mals belonging to the sea, I would consider 

 them rather as bred in the numerous fresh- 

 water lakes, that in primeval times covered 

 the face of uncultivated nature. Some of 

 these shells we know to belong to fresh wa- 

 ters; some can be assimilated to none of the 

 marine shells now known ;" why, therefore, 

 may we not as well ascribe the production of 

 all to fresh waters, where we do not find 



them, as we do that of the latter to the sea 

 only, where we never find them ? 



We know that lakes, and lands also, have 

 produced animals that are now no longer ex- 

 isting ; why, therefore, might not these fossil 

 productions be among the number? I grant 

 that this is making a very harsh supposition ; 

 but I cannot avoid thinking, that it is not at- 

 tended with so many embarrassments as 

 some of the former, and that it is much 

 easier to believe that these shells were bred 

 in fresh water, than that the sea had for a 

 long time covered the tops of the highest 

 mountains. 



CHAPTER VI. 



OF THE INTERNAL STRUCTURE OF THE EARTH. 



HAVING, in some measure, got free from 

 the regions of conjecture, let us now proceed 

 to a description of the earth as we find it by 

 examination, and observe its internal compo- 

 sition, as far as it has been the subject of ex- 

 perience, or exposed to human inquiry. These 

 inquiries, indeed, have been carried but to a 

 very little depth below its surface, and even 

 in that disquisition men have been conducted 

 more by motives of avarice than of curiosity. 

 The deepest mine, which is that at Cotteberg 

 in Hungary, b reaches not more than three 

 thousand feet deep; but what proportion does 

 that bear to the depth of the terrestrial globe, 

 down to the centre, which is above four thou- 

 sand miles? All, therefore, that has been 

 said of the earth, to a deeper degree, is 

 merely fabulous or conjectural : we may sup- 

 pose with one, that it is a globe of glass ; c 

 with another, a sphere of heated iron; d with a 

 third, a great mass of waters ; e and with a 

 fourth, one dreadful volcano : f but let us at 

 the same time show our conciousness, that 

 all these are but suppositions. 



Upon examining the earth, where it has 

 been opened to any depth, the first thing that 



Hill's FossUs, p. 41. b Boyle, vol. iii. p. 240. 



<= Buffon. Whiston. 



occurs, is the different layers or beds of which 

 it is composed ; these all lying horizontally 

 one over the other, like the leaves of a book, 

 and each of them composed of materials that 

 increase in weight in proportion as they lie 

 deeper. This is, in general, the disposition 

 of the different materials, where the earth 

 seems to have remained unmolested ; but this 

 order is frequently inverted ; and we cannot 

 tell whether from its original formation, or 

 from accidental causes. Of different sub- 

 stances, thus disposed, the far greatest part 

 of our globe consists, from its surface down- 

 wards to the greatest depths we ever dig or 

 mine. 6 



The first layer, most commonly found at 

 the surface, is that light coat of blackish 

 mould, which is called by some garden earth. 

 With this the earth is every where invested, 

 unless it be washed off by rains, or removed 

 by some other external violence. This seems 

 to have been formed from animal and vege- 

 table bodies decaying, and thus turning into 

 its substance. It also serves again as a store- 

 house, from whence animal and vegetable 

 nature are renewed ; and thus are all vital 



e Burnet. f Kircher 



e Woodward, p. 9 



