336 Mr. Toulmin Smith on the different Beds 



in the proper sense of the word, a mere accident, in no way neces- 

 sarily indicative of any change in geological deposit, and one 

 which might happen, and in fact has happened, during the course 

 of very different formations, and, as indeed the flinty chalk itself 

 proves, at varying periods during the course of any one deposit*. 



We may however find other characters, sufficiently well-marked, 

 which lead to positive and well-defined divisions of the white 

 chalk. Passing over minor subdivisions, three great divisions 

 force themselves upon the observer's attention where the chalk is 

 fully developed, as in the hills and valleys of Kent. These divi- 

 sions may be stated as — 1. the upper chalk, which happens to 

 coincide pretty exactly [though by no necessity, as above indi- 

 cated] with the chalk having horizontal layers of flint, and may 

 therefore be readily distinguished at a glance; 2. the middle 

 chalk, a chalk as white as the upper chalk and lying immediately 

 beneath it; and 3. the lower chalk, which, when wet, has a slightly 

 grayer tinge, though, when dry, not thus distinguishable from 

 either of the above. It is not unimportant to notice, that the 

 distinction drawn by Mr. Lyell (p. 386) between soft white chalk 

 and hard white chalk is a distinction which will not hold. The 

 upper, middle, and lower chalk is, quite indifferently, hard or 

 soft in different places. There are places in which the middle 

 chalk is so extremely rotten that it is almost impossible to extract 

 any fossil entire. This very chalk, again, by long exposure to 

 the atmosphere, becomes so extremely hard that it will turn the 

 edge of any tool, and is, from its extreme hardness, as imprac- 

 ticable as before from its rottenness. 



These three beds are to be distinguished by their organic con- 

 tents. It is not my present purpose to enter in detail into these ; 

 it is sufficient to call attention to the divisions by a few broad in- 

 stances. The most unpractised eye will at once perceive the dif- 

 ference in the groups of Terebratulce found in the three several 

 beds. The distinctions, not merely modifications, but in marked 

 characters, between the Echinites is very great ; while the Inoce- 

 rami offer the means of no less broad comparison. These last 

 abound, in extraordinary number and variety, in the middle 

 chalk. The abundance and character of the remains of the ver- 

 tebrate animals afford no less important means of marking these 

 divisions. I am however for the present content to rest the di- 

 stinction between the three beds upon the differences presented 



* Mr. Lyell states (as above, p. 386) these layers to be " from two to 

 four feet distant from each other." It will, however, be found, in fact, that 

 the differences are much more striking. I am acquainted with localities in 

 which several successive beds are found varying from one to two feet apart, 

 or less, — underlying which is a mass of chalk, without any layers of flints, at 

 least fifteen or twenty feet thick, but below which last other regular layers 

 of flints are found. See vol. xix. of this Journal, p. 15, note. 



