1815.] An Essay on Rents. Alt 
nearly 2 Ib. in weight, one end of which has the colour and pro- 
rties of the Bovey coal, and the remaining portion in the state of 
et. These ligneous portions have, in their drying, split in different 
directions, and into these divisions sulphuret of iron has been 
sed. 
“It is a circumstance remarked by agriculturists, that when stiff 
clay lands are well limed, however carefully mixed and ploughed 
into the clay, in the course of time a series of hardened calcareous 
masses are formed, evincing that during the changes of the condi- 
tions of the argillaceous part, in its softening and in its drying 
stages, the lime becomes mechanically separated. 
I shall take the liberty of troubling you for a future number with 
some remarks on the results of the analyses I have made on the 
substance of this cliff, before and after its calcination. 
Iam, dear Sir, yours respectfully, 
C. H. WiLKINnson, 
———— eee 
Articie III. 
An Essay on the Shapes, Dimensions, and Positions of the Spaces 
in the Earth which are called Rents, and the Arrangement of the 
Matter in them: with the Definition and Cause of Stratification. 
By Mr. John B. Longmire. 
(Continued from p. 217.) 
On Surface Rents. 
I HAVE said that the earth’s features are owing to the unequal 
contraction of its matter: the object of the following essay is to 
rove this assertion. 
The dry land is generally divided into mountainous and flat 
ground. Mountainous ground consists of many long elevations and 
depressions, or mountains and valleys, which are generally situated 
in the following order: one range of mountains divides the moun- 
tain ground into two parts ; both of which last contain ranges that 
make with the principal ranges either right or acute angles; and 
sometimes either or both of them contain small ranges similarly 
disposed towards them as they are to the principal range. A range 
of vallies lies between two ranges of mountains. Ifa line be drawn 
round the principal range, that for the greatest part is parallel to it, 
but that shall cross all the secondary ranges at right angles. The 
surface line of these ranges in this direction will be well repre- 
sented by the undulating line abcd ef g, fig. 4, Plate XXXVUIL 
which line encloses three mountains, J, d, J; and leaves two valleys, 
c, e, between them. This alternation of mountain and valley is thus 
accounted for. The earth’s matter, before it had assumed its pre- 
sent degree of solidity, diminished considerably in bulk 5 and as its 
5 
