90 DISPOSITIONS, FRACTURES AND 



It is well known that certain marine worms which 

 live in sand and inhabit straight tubular shells, invari- 

 ably penetrate the sand in a vertical direction. Ana- 

 logous fossils found in the horizontal strata, pre- 

 serve the same vertical position. But where sucli 

 strata are inclined, the position of the animal is no 

 longer vertical to the horizon, although it preserves 

 its perpendicular position to the stratum ; indicating 

 the change of place which that has undergone since 

 it formed a part of the ocean's bed. Further, when 

 a concave shell subsides in water, it must necessarily 

 rest with its convexity downwards ; and thus the 

 shells of such animals of this form as have died on 

 submarine banks, are found in the mud, accumulated 

 in this position. But in the elevated strata of rock 

 in which such remains abound, they are found no 

 longer to regard the horizontal plane ; while their 

 position, on the contrary, respects those of the strata ; 

 offering a test, in cases of great disturbance, by 

 which the originally inferior part of any such stratum 

 may be determined. The same conclusion follows 

 from considering the positions of leaves in the strata 

 that accompany coal. In these cases, the flat side of 

 the leaf is invariably parallel to the plane of the stra- 

 tum, although it may often be vertical to the horizon ; 

 a position, it is sufficiently plain, in which such sub- 

 stances could not have been deposited from water. 



The general elevation of strata from the bottom 

 of the ocean being thus proved, it remains to inquire 

 respecting those varieties of appearance and of relative 

 position, which are either interesting in themselves, 

 or in their consequences, or which require for their 

 explanation the aid of other accessary causes. 



As strata may be elevated to the perpendicular 

 position by causes or forces the exact nature of which 



