276 Botanical Society of Edinburgh. 



dation," in its strictest sense, to be the removal of portions of the 

 earth's surface by water, so as to expose to view the rocks previously 

 concealed beneath that surface. He briefly adverted to the various 

 effects produced by running water ; but enlarged principally on the 

 action of the sea — that being the principal agent employed in the 

 destruction and reproduction of strata mechanically deposited in 

 water. To show the bearings of this, he explained the action of the 

 sea on certain coasts ; showing the manner in which the breakers 

 act on coasts composed of rocks of unequal hardness, and on others 

 which, from the peculiar position of portions of their component 

 strata, are more or less easily wasted by the waves. The manner in 

 which a country is affected by these operations, according as it may 

 be rising above or sinking beneath the waters, was expounded, and 

 the processes by which the debris thus won from the land is spread 

 abroad in the surrounding seas ; showing that periods of slow de- 

 pression are most favourable for the accumulation of great thicknesses 

 of strata and the preservation of organic remains — the reverse being 

 the case during periods of elevation. Mr. Ramsay applied these 

 principles to explain the geological history of South Wales and the 

 neighbouring counties, showing the amount of denudation that the 

 rocks beneath the new red sandstone had suffered at various periods. 

 This was illustrated by certain of the sections of the Geological 

 Survey of Great Britain, drawn on a true vertical and horizontal 

 scale of six inches to a mile. In these, the older disturbed rocks 

 beneath the new red sandstone (viz. coal-measures, carboniferous 

 limestone, old red sandstone and Silurian formations) were shown to 

 have been all bent and contorted together. He explained the prin- 

 ciples by which the curvatures of disturbed strata beneath the sur- 

 face are deduced ; and on these principles he had restored the curves 

 that the same strata (once having, in these districts, been continuous) 

 would follow if now joined above the existing surface of the 'land. 

 This gave an approximation to the quantity of matter removed by 

 denudation from above that surface — amounting over great part of 

 the country to ten or twelve thousand vertical feet of solid rock ; part 

 of which, on the outskirts of Wales and in Somersetshire, was re- 

 moved during the new red sandstone and liassic periods ; and the 

 greater part — viz. the interior of Wales — since the deposition of the 

 London clay ; — the seas of the oolite and cretaceous periods never 

 having penetrated into the interior of Wales. It was during tertiary 

 times that the removal of this great mass by sea denudation was 

 effected ; this denudation giving to the country its present contour 

 of hill and valley. — Athenceum. 



BOTANICAL. SOCIETY OF EDINBURGH. 



Feb. 11, 1847.— Dr. Greville, President, in the Chair. 



The following communications were read : — 



1. A letter from Capt. Portlock, giving a short account of his hor- 

 ticultural proceedings at Corfu, and suggesting the Convolvulus Ba- 

 tatas, or sweet potato, as a substitute for the potato ; the plant has 



