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the subject has this peculiar local interest, that it is, in all 
probability, closely connected with the important features of 
denudation, which influence the conditions of the strata of 
the Coal Formation, extending, as is well known, not only 
to the present surface, but to a considerable extent below 
the surface. Few persons have an idea of the enormous 
amount of this denudation, or of the clearness of the evidence 
by which it is established ; but abundant examples in the coal 
and lead mine districts show that a vast period of time, and 
the long-continued effort of stupendous agencies, could alone 
have produced the denudation which is so strikingly apparent. 
Connected with the subject of Denudation, is that of the 
deposit of Drift, or diluvial deposit ; and this strongly marked 
feature of our northern valleys is of great importance to 
the miner, inasmuch as the beds of coal are sometimes en- 
tirely cut off, or carried away, and their place supplied by 
such deposits ; and, as will be seen by the sequel, such 
deposits are known to have a great resemblance to, and pro- 
bably an immediate dependance on, the results of glacial 
action, as it is now to be observed in the valleys of Switz- 
erland and other mountainous countries. The cause of 
those vast masses of detritus — the tracts of country through 
which they run — the laws by which they are governed — are 
all matters of immediate and practical interest in a country 
where so much depends on an intimate subterranean know- 
ledge of geological phenomena ; and it is only by a close 
and long-continued investigation of the phenomena presented 
to us that we can hope to arrive at such knowledge. The 
study of the Glacial Theory may indeed be considered as 
extremely interesting, if it were only to afford to the general 
reader a correct notion of the phenomena of the Swiss 
Glaciers, as described by Agassiz ; it is of great interest 
to every tourist, by affording a constant subject for investi- 
gation in elevated regions, in traversing which for plea- 
