POPULAR SCIENCE REVIEW. 
274 
Lee, and many others, it becomes evident that they could not possibly 
have excavated their valleys since the limestone attained its present low 
level ; for, in every case, after draining the upper part of a valley, the 
river, instead of following its natural and shortest course over the lowest 
land to the sea, turns aside to cut through high bluffs of old red sandstone 
or older strata ; and if these deep channels were dammed up to the height 
of 200 or 300 feet, the rivers, instead of toppling over the obstructions, 
would have taken widely different courses. Yet Mr. Jukes, finding that 
these ravines are not along lines of faults or fissures, and failing to detect 
any signs of dislocation, believes that the existing rivers have worn their 
channels through the hills. 
Now, because there are many valleys in the “ old red ” exhibiting highly 
inclined carboniferous strata resting conformably on it, the conclusion is 
legitimately drawn, that the rocks of these parallel latitudinal valleys 
were once continuous, and have been denuded subsequent to the age when 
both systems of strata were thrown into great lateral folds. Similarly, 
because the isolated mountains of coal measures have the same dip and 
contain the same fossils, it is regarded as demonstrated — not only that 
the solitary hills were once connected by intervening rock of the same 
kind, but that the coal deposits once extended continuously over all the 
limestone. All this vast thickness of several thousand feet has then been 
removed ; and hence the ridges formed by contortion have all been cut off, 
and the country so far converted into a plain ; and it might be easily shown 
that this denudation could only be accomplished by the sea. Mr. Jukes 
believes that in all cases where the conntry is flat, and the beds are not 
horizontal, the open sea, by long continued action over it, has, “ like a 
gigantic planing machine,” removed the elevations. 
And thus it becomes evident that approximately the land rose up as a 
flat, over which, from the beginning of the upheaval, the drainage will 
have flowed from the peaks to the sea. And this necessarily implies that 
the deep valleys in the old red sandstone containing carboniferous lime- 
stone did not then exist, but that the carboniferous and old red rocks were 
at the same level. And the point of the paper is, that the wasting action 
of the atmosphere and rain is regarded as the cause which has removed 
the whole mass of the limestone to a depth of 300 feet, and so formed the 
valleys. For had these valleys been filled up, the rivers would have taken 
their present courses over the old red sandstone to the sea ; and as the 
river and atmosphere acting together would necessarily be a more potent 
power than the atmosphere alone, it is conceived that the rivers would deepen 
their beds faster than the rate at which the level of the limestone descended. 
But as these limestone valleys were formed, they produced lateral rivers 
of their own, flowing to the east, and these were, of course, received as 
tributaries where they reached the original steam ; but from draining a 
much larger area, the feeder was larger than the river, and now has the 
appearance of being the river itself. 
Such is the theory ; and it certainly accounts satisfactorily for the 
existence of the deep tortuous ravines through which the rivers flow. 
While there is no difficulty in the thickness of rock removed, except the 
trifling consideration of the lapse of time it must represent, for in county 
