426 SKETCH TOWARDS A 



rential superposition, not less hypothetical ; while this 

 is the only one in which there is ample ground for 

 doubts : the mode of production of a single stratum, 

 the coal, furnishing a point of departure not to be mis- 

 taken. 



It is now again plain, that a depression similar to 

 the last must have occurred, to permit the deposition 

 of the remaining strata, up to our highest marine sur- 

 face, the chalk, or more, if more there be; and thence, 

 in the same way, I must deduce a twelfth condition in 

 the earth; the consequence, under similar hesitation 

 as to its extent, of another distinct revolution. And 

 the carboniferous surface of the green sand is now be- 

 neath the ocean ; undergoing the change to coal. It 

 is only further needful to suggest, that although nei- 

 ther of these last acts of elevation should be admitted, 

 yet that a continuous depression from the carbonife- 

 rous surface of the oolithe to that of the chalk will not 

 explain the appearances : because the production of 

 the upper lignite, like that of the lower, marks a long 

 repose, and there must therefore have been two dis- 

 tinct depressions. And that the act by which the lower 

 lignite was depressed, was one of revolution, is proved 

 by the disappearance of organic fossils, or of Life, in 

 the green sand : that fact which I had formerly stated 

 as an unexplained one in the Theory of the Earth. 

 Whether it produced irregular positions of the strata 

 any where, geology does not yet know, and must not 

 assume of all places. And surely I need not here re- 

 peat, that although the whole of these views of the 

 conditions of the earth might be nullified by the an- 

 tient hypothesis of " the rising and falling of the ocean," 

 'this has been sufficiently proved to be impossible. They 

 would also be nullified, should there be no real super- 

 position from the coal upwards, and should the whole 



