202 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 5, 
Highlands. This appears not only from the comparison of the two 
formations, but also from the character of the sandstones in the 
central district of Scotland, which have undoubtedly been produced 
by the wearing-down of the primary rocks in the north. It seems 
thus more probable that these beds have resulted from the waste of 
formations of clay-slate and greywacke, not much unlike in their 
general characters to the formation now under review. ‘This is an 
interesting fact on several accounts. It shows that our present sedi- 
mentary deposits were not the earliest rocks of that character on the 
globe, or rather in this portion of it, but were preceded by other 
masses, like them produced from the destruction of a still earlier for- 
mation. In this district it is therefore possible to intercalate between 
the oldest existing strata, and the oldest rocks of which any trace 
remains, another stratified formation, composed of sedimentary ma- 
terials. The transition rocks in the south of Scotland are thus the 
third in order of formations, whose existence is established by facts. 
And it must be observed that these formations do not resemble the 
separate deposits of the secondary system in England, one of which 
is regularly superposed on the other, so that both may have derived 
their materials from the same source, but are formations each of 
which implies not only the previous existence, but also the consolida- 
tion and destruction of that which preceded it. Mineral geology is 
thus able te carry us a step farther back into the history of the globe, 
than we can proceed on the evidence of organic remains, and shows 
that the revolutions which these remains attest were not the first, but 
the last in a series to which no definite limits can be assigned. 
The existence of an earlier series of sedimentary rocks leads to some 
other conclusions to which, though of a theoretical character, we 
must shortly allude. So far as we can ascertain, the depths of the 
ocean are the spots where rocks are deposiced and formed, whilst the 
dry land and the sea-shore are the places where they are destroyed 
and wasted away. ‘There is not any known process now acting on 
the globe by which the rocks existing in the depths of the ocean could 
be disintegrated and their detritus formed again into newrocks. Any 
ancient sedimentary deposit therefore implies not only the existence 
of a sea in which its materials were deposited, but of a land from 
which they were derived, and rivers and currents by which they were 
carried down to that sea and spread out over its channel. This con- 
clusion is so self-evident that we should not have alluded to it, had 
not the opposite doctrine been sometimes maintained, and the as- 
sumption boldly made, that at the time of deposition of the Silurian 
formations dry land and consequently land animals and plants did 
not exist. These beds themselves we now see teach a different 
doctrine, and show that even then there must have been dry land 
watered by showers of rain and traversed by rivers; may we not also 
infer from the analogy of existing nature, clothed with its appropriate 
vegetation and inhabited by its peculiar tribes of animated and sen- 
tient beings ? 
The cause of the present highly-inclined position of these strata 
is an inquiry of much interest, but on which little certainty can be 
obtained. In the beautiful section of this chain of mountains at its 
