THEORY OF THE EARTH. 427 



vertical sequence from the red marl to the chalk be 

 hypothetical instead of actual, as part of it assuredly is. 

 But I must believe, with other geologists, that there is 

 enough proved for this purpose ; although I have not 

 seen all that I could wish respecting these strata. 



If the intricacy of these last changes has demanded 

 some space, what follows is comparatively simple, as it 

 is indisputable. What numerical order the necessary 

 revolution should hold, must now be doubtful ; but it 

 was an extensive and a great one ; since by this was 

 the inferior coal elevated, with all that was needful, 

 beneath it, and with all that now exists above ; ex- 

 tending, certainly, to the chalk, and probably to some 

 superior strata, in particular places at least: while, this 

 defect in our knowledge leaves another blank to be 

 supplied, as to a perfect theory. And this condition, 

 though assuredly not the exact Earth which we in- 

 habit, is at least the basis of the present order of things, 

 as it is a thirteenth condition. 



But here the difficulties of discovering a just theory 

 are renewed. There has been a subsequent revolution, 

 or there have been more than one: but which of these 

 is the fact, our knowledge does not yet enable us to 

 determine. The condition of that Earth which is, at 

 least, a fourteenth one, diifers from the preceding in 

 those two essential facts which constitute the elevated 

 " tertiary" formations, together with the Italian, and 

 probably some other, alluvia. But, at present, we have 

 no evidence to prove whether there was, here, one re- 

 volution, or more, with corresponding conditions of 

 the globe, and, therefore, an Earth, or Earths, different 

 from the preceding, and anterior to the creation of 

 Man. Whether this blank will be filled, or not, here- 

 after, I am unable to foresee ; and it is not here my 

 business to suggest the means. It is sufficient, that 



