1815.) An Essay on Renis. ais 
covered with the lake and alluvial matter, so that the steep side Ai, 
which corresponds with the steep side i /, cannot be seen. 
All the rents in @ group of mountains are resolvable into some of 
the foregoing rents: and all mountains and vallies are composed of 
some one, or combinations of two or more of, or all, these natural 
or rented inequalities. When a mountain is separated into parts by 
Surface rents, the common, or undulated figure, is often disguised, 
or rather altered ; but a sufficient resemblance still remains between 
its figure as it appears at present, and what it was before these rents 
happened, to distinguish the original extent and shape of every 
mountain. Where mountains and valleys are small undulated in- 
. . .  * . . . eye 
equalities, as in the primitive district of Cornwall and Devonshire, 
surface rents are wanting ; and from this circumstance arises the 
tameness of the scenery in these parts; but in the mountains of the 
northern parts of England and Scotland the undulations are much 
higher, and of course surface rents abound, and give the charac- 
teristic sublimity to these mountains. 
I have hitherto confined my remarks to the primitive mountains. 
The mountains of transition lime-stone have steep sides which 
generally face the primitive mountains, and flat sides next the floetz 
or stratified countries ; but sometimes the steep side faces the stra- 
tified formations, and occasionally any point between the primitive 
and stratified formations. ‘This difference in the position of the 
Mountain masses of lime-stone is thus accounted for. When the 
lime-stone lies on the remote side of a mountain range, whose long 
direction is parallel to that of the principal mountain range, the 
steep side faces the centre of the mountains: and when it lies on 
that side of such a mountain which is nearest the centre of the 
ptimitive group, its steep side then faces the stratified formations ; 
but if it lie on either side of a mountain whose position is at right 
angles to that of the principal range, its steep side neither faces the 
centre of the group, nor directly the stratified formations, but a 
place half way between these extremes. The reason why mountain 
masses of lime-stone, lying only on one side of primitive mountains, 
must have steep and flat sides, will appear on examining the dia- 
gram attached to fig. 4. The floetz formations have undulated in- 
equalities also, but they are much smaller than those of the primi- 
tive matter, The smallness of these inequalities is owing to the 
following circumstances: a collection of the floetz formations lies 
in very large hollows of the primitive and transition matter. Hence 
as this hollow was forming and filling slowly and progressively, the 
Yower half had time to acquire a considerable degree of solidity, so 
that when tlhe hollow was filled it was mostly the unequal contrac- 
tion of the matter in the upper half of the formations that could 
affect the surface; and the inequality in the contraction of this part 
would give rise to only small elevations and depressions. When 
either the tops of isolated, underlying, unstratified, mountains, 
which are composed either of primitive matter, such as clay-slate, 
