1815.} An Essay on Renis, S17 
same relation to one another as I have shown to be necessary to con- 
stitute stratification. 
’ After the matter on which all stratified formations ‘rest had 
assumed a small degree of solidity, it contracted unequally. Hence 
one ‘part of its surface sunk lower than another, and gradually 
formed a number of hollows, into which as gradually entered 
originally fluid matter, and matter greatly comminuted and mecha- 
nically suspended in water. 
Let us endeavour to follow the formation of a hollow through a 
few stages. Let A, fig. 3, be the first stage. Here a hollow, say 
of a few feet in depth, is observed, which has been gradually 
formed by the sinking of one part a lower than the part de. Let 
B be the second stage. The hollow has now got an additional area 
marked J, and is twice the depth that it was at the end of the first 
stage, with an equal increase of dimersions sideways, Between 
this stage and the first the hollow has been gradually increasing in 
dimensions by the sinking of the part a J more than the part de. 
C is the third stage; in which another space ¢ is added to the 
hollow. In this manner the extension of the hollow weuld continue 
as long as the matter continued to contract unequally, or till the 
earth had acquired its present degree of solidity. Some hollows are 
filled with matter of one denomination, as white sand-stone, &c. ; 
others with that of various denontinations, as in the coal formations. 
‘The matter in the former instance has proceeded from one source ; 
in the latter, from different sources. Some hollows, again, were 
filled with matcer while forming; others not till after they were 
totally, or at least nearly, formed. But all hollows so produced, 
and filled, and such spaces only, except a few rents, contain matter 
having the stratified structure. ‘The slow but gradual entry into 
hollows of matter either fluid or mechanically suspended in water, 
is certainly necessary to give to such. matter the stratified structure ; 
but if these hollows had not been formed by. the unequal contrac- 
tion of the matter below them, the present stratified matter would 
have remained for ever in its original situation. Stratification, then, 
in this point of view, is aweflect of the unequal contraction of the 
earth’s matter, 
