334 Notice and Review of the Reliquiae Diiuvianae. 
lest doubts as to the evidence there is to prove that the 
surface of the earth owes its last form not to the gradual 
action of existing causes, but to the excavating force of a 
suddenly everwhelming and transient mass of waters.?? __ 
We must not, however, attribute the origin of all vallies 
to diluvial action. In primitive and mountainous districts 
especially, ‘‘ the original form in which the strata were 
deposited, the subsequent convulsions to which they have 
been exposed, and the fractures, elevations and subsiden- 
ces which have affected them, have contributed to produce 
vallies of various kinds on the surface of the earth, before 
it was submitted to that last catastrophe of an universal 
deluge which has finally modified them all.” 
Existing vallies, then, have been produced by three dis- 
tinct classes of agencies. 1. By the present streams, the 
bursting of lakes, &c. 2. By the last universal deluge. 
3. By the original construction of the strata, and diluvial 
actions previous to the last. It may be difficult, in all 
cases, to refer the origin of particular vallies to its proper 
period. It is sufficient, however, for the purpose of this 
argument, to show, that there exist cases clearly referable 
to all the agencies above mentioned. When, for instance, 
we find on the margin of a valley, diluvial pebbles and 
bowlders, evidently torn out of that valley, we can have no 
hesitation in ascribing its excavations to the last universal 
deluge. ' 
Excavations formed by that catastrophe are called 
*¢ vallies of denudation.” Mr. Buckland has presented us 
with an account of several of this description, existing 
in Europe. But plates and maps are almost indispensable 
to a clear conception of cases of this kind ; and, therefore, 
we can only recommend to our readers the perusal of the 
Appendix to this work. The subject, we believe, has re- 
ceived in this country little or noattention. There can be 
no doubt, however, that these extensive regions furnish 
many interesting instances of vallies produced by diluvial 
action. They are to be sought after, with the greatest 
prospect of success, in our newest formations. We are 
acquainted with one clear instance of the kind, near Con- 
necticut river ; but we cannot make it understood without 
a map and sections ; and if we mistake not, we discover, 
