lii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Zamites as the oolitic coal of Yorkshire ; and further below there are 

 sandstones of an age not at present determinable. It is remarkable, as 

 pointed out by Mr. Sharpe, that, in looking at the correlation of these 

 beds with better-known deposits, the approximation decreases as 

 the beds become more recent ; as for example, in the cretaceous 

 (or Hippurite) series 45 per cent, of the fossils are described species, 

 in the subcretaceous 53 per cent., and in the Jurassic 84 per cent, j 

 and on this Mr. Sharpe observes, that, whilst the species common at 

 each epoch to Portugal and Northern and Middle Europe afford 

 evidence of diminishing facilities of intercommunication as time pro- 

 gressed, it would be rash from such a fact to build up an argument 

 for the greater diffusion of species at earlier epochs without having 

 previously studied the habits, and powers of migration, of the animals, 

 the relics of which they are. 



1854. — Mr. Sharpe read a paper on "The Structure of Mont 

 Blanc," to which I shall have occasion to refer at a later period of 

 my address. In it he dissents from the views of Professor James 

 Forbes, as regards the superposition of the granite of the Alps upon 

 secondary rocks. 



1855. — In a paper read Dec. 5, Mr. Sharpe made a bold attempt to 

 determine, by the supposed marks left by the sea on the sides of the 

 Alps, the age of the last elevation of that mighty mountain-chain. 

 Instead of explaining the erosion of the surface visible to a great 

 height, as Agassiz had done, by the action of glaciers, Mr. Sharpe 

 confines the action of glaciers to valleys, and assumes that ancient 

 glaciers had never extended more than 3000 feet below the present 

 limit of glaciers, thus rendering it necessary to seek for some other 

 cause of erosion at levels above and below certain limits, and specially 

 for that deep erosion which he considers incompatible with the action 

 of moving ice at all. This erosion he ascribes to the action of the 

 waves of the sea whilst washing the base of the rocks, and notes 

 three several lines at which the sea must be supposed to have rested 

 sufficiently long for the production of such an effect. The first of 

 these is at the height of about 9000 feet ; the second at about 7500 

 feet, which can be traced through a great part of the centre of Switzer- 

 land (and which Professor Forbes considered the upper limit of ero- 

 sion), cutting through the nummulitic as well as the Jurassic rocks ; 

 and the third line of erosion at 4800 feet. Mr. Sharpe further as- 

 cribes the later degradation of the Alps, the removal of large masses 

 and the formation of Alpine valleys, to the same cause, namely, the 

 wear of the sea, aided by the denuding force called into action by the 

 sudden changes of level, previously mentioned ; and then, coordi- 

 nating with the levels of the lines of erosion the different elevations 

 above the sea at which valleys terminated and terraces were formed, 

 he obtained a similar result to that which he had already deduced 

 from observing the lines of erosion alone : namely, that, after the 

 Alps had attained their present form, and when they stood as much 

 above the surrounding country as at present, they were once more 

 nearly submerged below the sea, and then were raised again out of 

 it by several steps or comparative starts, after each of which was 



