205 
in Mr. Lyell's Principles of Geology, a work which has been 
held in deserved estimation for many years. It only remains 
to be proved that we have grounds for attributing the appear- 
ances which I have described to its action. 
There can be no doubt that some different conditions 
would be required to produce the alleged alteration in cli- 
mate. The relative proportions of land and water are proved 
to have a great effect, not only upon the temperature, but 
also upon the humidity and transparency of the atmosphere ; 
and that various causes combine to determine the limits of 
perpetual snow, is evident from many facts detailed by Mr. 
Darwin, in the work before alluded to. 
Referring you again to the 1st vol. of Mr. Lyell's Prin- 
ciples, you will there find proofs that at the commencement 
of the tertiary epoch a large proportion of Europe was sub- 
merged : this is in strict accordance with the acknowledged 
fact of the gradual elevation of land. Now, supposing that 
at the period when the erratic boulders were removed from 
their original site, the land had not attained its present ele- 
vation, (say by only 200 feet) and the occurrence of recent 
shells at a great height above the level of the sea fully 
warrants that supposition, let us imagine what effect this 
change of level would have upon the contour of England, 
and more particularly of this district. All the lower parts of 
the country would be under water ; the mountains of West- 
moreland and Cumberland would form a centre, from whence 
elevated ridges would radiate; the range of which Black- 
stone-edge is a part, with all its numerous branches, would 
form a tract of high land, while the valleys of the Tees, the 
Swale, the Ure, the Aire, and the Calder, would be narrow 
arms of the sea, penetrating far into the land, for none of 
these rivers rise rapidly until they approach their sources. The 
vale of York would be a shallow channel, beyond which the 
Northern Moorlands and Wolds would rise above the waves. 
