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difficulties which have hitherto surrounded our inquiries ; and 
this brings me to a consideration of the keenly disputed 
glacial theory. 
Many years since Mr. Lyell attributed the removal of 
erratic blocks to the agency of floating ice, and adduced 
other proofs of the former existence of a greater degree of 
cold than now obtains. In this view he has been supported 
by Mr. Murchison and some other geologists, but the subject 
did not gain general attention in this country, before the pub- 
lication of M. Agassiz's observations on the glaciers of the 
Alps. After reading a paper descriptive of the phenomena 
which they exhibit, at the Glasgow Meeting of the British 
Association, he travelled through a considerable part of 
Scotland, in company with Professor Buckland, when he 
discovered many evidences of the former existence of intense 
cold. 
The hillocks of detritus which occur in such immense 
abundance in many parts of his route, were pronounced by 
him to be identical with similar mounds now formed in the 
valleys of the Alps, by retreating glaciers, and which are 
known by the name of moraines, 
A few miles above Middleton-in-Teesdale, on the division 
line of Yorkshire and Durham, are some very good examples. 
The ranges of hills on each side of the valley are flanked by 
smooth terraces of removed matter, completely concealing 
the true strata of limestone and sandstone, which form bold 
angular projections when left bare ; and in many places 
large mounds, sometimes of such magnitude as to claim the 
appellation of hills, obstruct the course of the river, which 
has to wind its devious way at their feet. The miners have 
given the name of " slipped stuff" to this detritus, which con- 
tains many boulders of the harder rocks, as the basalt of 
Caldron Snout, interspersed amid a mass of finer matter, 
resulting from the disintegration of the softer rocks. In the 
