340 



THE GEOLOGIST. 



generally of nearly five hundred feet, and that these flowed from the peak down 

 those six lateral valleys we have already mentioned. From his own observa- 

 tions he estimates the greatest formerly attained thickness of ice at the Pass 

 of Llanberis at from eleven hundred to thirteen hundred feet. 



We are now introduced to another phase of the subject, the relations of the 

 glacial drift to the glaciers. Everyone M'ho has given any attention to tertiary 

 geology is aware that a large portion of the low country of the North of 

 Europe and a considerable portion of the British Isles are covered more 

 or less by loose superficial detrital accumulations, containing large boulders 

 and rocks which have been brought often many hundi-eds of miles from their 

 original beds. These deposits are, as we might have presumed they would be, 

 regarded by the Professor, according to the modern glacial theories, as the pro- 

 duce of melted icebergs. 



This glacial di'ift rises to very considerable heights (upwards of two thousand 

 feet, and containing shells at thirteen hundred feet) above the sea in tliis Snow- 

 donian region; and much of it, though rudely stratified, resembles ordinary 

 moraine-matter. Erom its arrangement in terraces it is considered to mark suc- 

 cessive stages of elevation of the land in its emergence from the glacial waters ; 

 and that as the average height of the loftiest mountains could not during that 

 era have attamed more than from fourteen hundred to two thousand feet, the 

 formation of glaciers upon them proves the intensity of the cold at that period. 

 Erom these glaciers icebergs broke off at the sea-board, strewing the regions 

 around in their dissolution with rock-boulders and drift-gravels. 



Some remarks follow on the grinding and scooping out, by the glacier in its 

 motion, of the hollows since converted into lakes and tarns ; and the paper is 

 concluded by some speculations on the possibility even of the eyes of man hav- 

 ing gazed on those old glaciers of Wales. 



A chapter on Etna and some suggestions for Alpine travellers finish this 

 excellent and tasteful book, which we hope will have very many readers, for 

 the reason that it can neither be read without interest nor without profit ; and 

 we are pleased to observe that a second edition is abeady called for. 



Map of Hereford. By T. E. Cuuley, Esq., C.E. 



We gladly notice this map, sent to us a short time since by Mr. Curley ; for, 

 although a local production, and consequently limited in its uses and applica- 

 tion, it presents a step in a right direction, which, if followed out m like 

 mamier in other districts, would render material aid to a very extended and 

 minute knowledge of the stratigraphic condition of these islands. Mr. Cur- 

 ley, engaged upon the drainage of the town of Hereford, has necessarily met, 

 in the execution of the works he has been superintending, with numerous 

 opportunities of acquiring an intimate knowledge of the rocks and soils of that 

 town and its vicuiity. Some of the information thus obtained, carefully worked 

 out into two sections exhibiting the disposition of the gravels and local drift- 

 beds on the adjacent new red-sandstone, have been added with good effect to 

 the map. We hope other engineers will follow tliis excellent plan, and that, 

 ere many years, all our to"\vn plans wiU. have as much geological information 

 appended to them. The practical value of such additions cannot be over- 

 estimated. 



