250 Proceedings of the British Association. 



tion of laws. Nor did he feel any difficulty arising from the number 

 and complexity of these changes, since they had been eifected in an 

 eternity of past time, with the hand of Omnipotence to work in it. — 

 Dr. Buckland remarked that the coal-measures must have suffered 

 a great amount of denudation since the displacements which the stra- 

 ta had undergone were not visible on the present level surface. Sir 

 James Hall had constructed similar sections to those of Mr. Ramsay's, 

 demonstrating that many thousand feet of strata had been removed, 

 as he supposed, at the time of the upheaval of the country, by the 

 action of waves upon the broken summits of the hills. Dr. Buck- 

 land considered that in many places the denuded strata had not been 

 so thick as in those where they still remain, because the most exten- 

 sive formations were local, and thinned off towards their shores. 

 His greatest difficulty was in accounting for the wreck of these 

 formations, there being no adequate amount of detritus visible in any 

 of the newer formations. In some strata pebbles were exceedingly rare. 

 He did not think much importance could be attached to the climatal 

 character of fossil insects ; he had himself seen on the perpetual snow 

 of Etna the insects of the warmer regions below : but if, as supposed 

 by Mr. Ramsay, there had been in Wales mountains 15,000 feet 

 high, at the period of the London clay, it might remove in some de- 

 gree the objection to his theory respecting the existence of glaciers 

 in that country at a somewhat later period. — Mr. Hopkins discussed 

 the mechanical causes of the phenomena of elevation, to determine 

 whether these had resulted from a gradual and progressive force, or 

 from reiterated paroxysmal action, requiring attention not only to the 

 character of the elevation, but also the phenomena of denudation. 

 With respect to the direction of the force, the greatest difficulty 

 was in accounting for the horizontal thrust indicated by the contor- 

 tions of the strata ; if wave-like undulations were produced in a semi- 

 fluid below the surface, as conjectured by Prof. Rogers, they might 

 be communicated to the solid crust, but such a condition was dyna- 

 mical, and would not necessarily produce any permanent results ; 

 but if the whole undulating area were elevated simultaneously and 

 then subsided, certain portions would sink down more than others, 

 and from the pressure of the arches thus constituted an unlimited 

 horizontal force would be produced, — within, however, certain fixed 



