91 



whilst he agrees with Mr, Hopkins respecting the comparatively mo- 

 dern origin of the existing lakes and valleys, he does not believe 

 with him that the whole of the valleys were formed posterior to 

 the Mountain Limestone. On the contrary, he thinks that there 

 are rudiments of diverging valleys of an older period. Professor 

 Sedgwick must also I presume reject the hypothesis of the Mountain 

 Limestone having at any period been deposited as a continuous ealca- 

 I'eous sheet upon the older rocks, for he has expressed his belief that 

 the limestone was accumulated as an external fringe like a vast 

 coral reef around a cluster of more ancient rocks. ' • 



But whatever may be their differences on these points,, I have rear 

 son to think that Professor Sedgwick entirely concurs with Mr. Hop- 

 kins, in the necessity of calling into play enormous aqueous currents 

 (which followed elevations) to account fof much of the coarse drift 

 which has been poured off upon the flanks of this mountain chain. 

 Unwilling to call in the assistance of icebergs, and opposing the hy-- 

 pothesis of a depression of temperature, Mr. Hopkins shows, that the 

 propelling forces of water alone are fully adequate to produce the 

 transport of all the blocks and gravel around the Cumbrian chain? 

 and to spread them out in the great masses of drift which encumber 

 the adjacent northern centres, accounting for the existence of diver- 

 ging currents by a number of paroxysmal elevations. Assuming 

 moderate upheavals of certain areas of land, to a height of 50 feet 

 egxih, from beneath an ocean having a depth of 300 and 400 feet only, 

 he informs us that a number of great divergent waves would be the 

 consequence. 



In describing the motion of such masses of water, he invokes the 

 aid of those waves of " translation " whose properties have been rer 

 duced to laws by the ingenious and valuable researches of Mr. Scott 

 Russell, and who, giving us measures of their relative velocity .an(J 

 power, has brought forward exact proofs of the transference by them 

 of solid bodies immersed in water. Such waves have in fact been 

 generated by the experiments of Mr, Scott Russell, exactly in iche 

 same way as Mr. Hopkins supposes waves to have originated on 

 the great geological scale. These experiments prove, that a sudden 

 elevation of a solid mass from beneath the water, causes a corre- 

 sponding elevation of the surface of the fluid, which infallibly pro- 

 duces a wave of translation t)f the first oi'der. Now this wave is 

 termed one of translation, because it is found not to rise and fall 

 like common waves, but wholly to rise and maintain itself above 

 the level of the water. Arguing that this wave is propagated with 

 a velocity which varies with the square root of the depth of the 

 ocean, Mr. Russell determines the velocity of wave transmission ; 

 but what is of most importance to the geologist is, that the old idea 

 of the agitation and power of waves extending a little way down only 

 in the sea, is found to be not true as touching waves of translation ; 

 for Mr. Scott Russell has ascertained that when they are in action, 

 the motion of the particles of the water is nearly as ff r eat at the bottom 

 as at the top. He further shows, that the body moved at the bottom, 

 is not rolled backwards and forwards as by a common surface-wave, 



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