22 PRINCIPLES OF GEOLOGY. 



strata, which must necessarily have been at first deposited nearly horizon- 

 tal. Therefore, such rallies were not produced till after the displace- 

 ment of the rocks. 



No one has carried his speculations on this subject so far as Dr. 

 Hutton, who maintained that vallies were, in all cases, scooped out by 

 the streams which run in them.* This is a characteristic part of his 

 system of decaying and renewing worlds, and whoever views the minute, 

 though not imperceptible, effects of our rivers, need not cavil at the 

 ample time he allows for their producing such effects as the denudation 

 of vallies. But this opinion clashes so directly with plain facts, as to 

 be wholly inadmissible. How can we apply such an hypothesis to those 

 numerous vallies in the plains of chalk in Yorkshire, Wiltshire, and 

 Dorsetshire, which have never carried water in the memory of ages, 

 down which, indeed, no trace of a channel can be seen ? Yet they are 

 branched like the vallies of other districts, have all their sinuosity of 

 course, and regular declination, but the soil and stratum are too ab- 

 sorbent to be moistened by the most hasty, rain. 



The excavation of vallies can be ascribed to no other cause than a 

 great flood of water which overtopped the hills, from whose summits 

 those vallies descend. Such a flood, put in violent motion, might, we 

 may svippose, by its currents and eddies, scoop hollows which afterwards, 

 on its retreat, would be extended in long connected vallies. From the 

 best and most independent evidence we have shewn, that such a flood 

 has once overflowed the earth since the consolidation of its surface ; 

 and as we have no proof of more than one such flood, and as there seems 

 to be no contrary evidence, it is probably to the deluge we must ascribe 

 the excavation of vallies. 



But the deluge has long passed away, and other events have materially 

 changed the face of the earth. Did not the voice of history and tradition 



* Quodque fuit campus, vallem decursus aquarum 

 Fecit. . i . OVID, METAM. xv. 



