MODE OF DEPOSIT OF COAL. 439 



the idea of any deposit of so attenuated a nature having 

 been spread over spaces so large by the act of drifting. 



4. On the other hand, the size of many of the coal-seams, 

 considered with reference to the immense compression which 

 they have unquestionably undergone, is considered to furnish 

 another objection of insurmountable character. The enor- 

 mous extent to which the bulk of substances may be reduced 

 by pressure, can scarcely be imagined, except by a reference 

 to exact computation. It was ascertained by Mr. Burr that 

 a mass of rubbish which was left in a worn-out vein of iron- 

 stone, during a period of two years, was in that interval 

 reduced from seven to two feet in thickness, owing to the 

 pressure of the overlying weight. It was further changed 

 into so hard a substance, as to form a mass of rock, which 

 could only be penetrated by the operation of blasting. 

 When we consider the great compressibility of vegetable 

 matter, and reflect that beds of coal have been subject to the 

 pressure of masses of rock many thousand feet in thickness 

 during a period of countless ages, and when we recollect 

 that matter so compressed has formed beds of great relative 

 thickness, it is evident that, for the formation of such deposits, 

 supplies on the most enormous scale would be required, and 

 that it would be utterly impossible to transport masses of 

 vegetable substance so immense as would be requisite for 

 the formation of the coal deposit alone. 



5. The high state of preservation in which many of the 

 plants occur, the perfect condition 'of the leaves, and parts 

 of fructification of many of the ferns, the sharp angles of 

 numerous stems which are presumed to have been of a soft 

 and succulent nature, with the surfaces of Sigillarice marked 

 with lines, streaks, and flutings, so delicate that the mere 

 drifting of a day would have inevitably destroyed them, 

 together with the occurrence of fruits, such as Cardiocarpon 

 and Lepidostrobus, which are found in heaps and clusters, 

 whereas a current would have dispersed them, these, with 

 other facts of a like nature, convince us that these plants 

 have never been subjected to drift, but were buried on the 

 spots where they lived and died. 



6. An additional objection to the drift theory is founded 

 on chemical facts; it has been urged, that if vegetable 

 matter were swept away by a flood, such an agency, by 



