MODERN VIEWS OF DENUDATION. 
By EDWARD HULL, B.A., E.G.S., of the Geological. Survey of 
Great Britain. 
I T is curious — as illustrating 1 tlie tendency of opinion to 
revolve upon itself — that in this year of geological science, 
A.Gr. 64, dating the epoch from the publication of Playfair's 
“ Illustrations of the Huttonian Theory," which I take to be the 
true birthday of modern geology — a fierce controversy should 
be waging on one of the fundamental principles of the science, 
the origin of denudation. Yet such is the fact. As it was in 
the days of Hutton and Werner, so it is in the latter days of 
Murchison and Lyell ; in both cases the geological world is 
divided into hostile camps — one party maintaining the atmo- 
spheric, the other the combined marine and atmospheric origin 
of valleys, and, by implication, of ridges and escarpments. 
The controversy, which was originally confined to the 
question of the valleys, has gradually expanded, so as to 
embrace the scenery and physical features of the surface — in- 
cluding plains, hills, terraces, and mountain heights ; which, 
according to one set of views, have been attributed mainly , 
though not exclusively, to the eroding and levelling 
action of the sea during the submergences of the land; 
and according to the other, have been produced by the long- 
continued action of rains, frosts, brooks, and rivers — all 
included under the category of " atmospheric agencies." 
These latter are the modern views, adopted with enthusiasm 
by several eminent naturalists, and, like most new doctrines, 
carried to extremes which the original propounders little 
dreamt of. The upholders of the older views occasionally 
come in for a sound rating* from the apostles of the new ; 
while others speak of the modern views as “ a revelation " ; 
and others go so far as to assert that in all cases of denuda- 
tion the onus probandi lies with those who maintain marine 
agency, in preference to atmospheric. Let us in the following 
pages endeavour to see what, on the one hand, are the grounds 
* See the Geological Magazine for July, p. 293. 
