340 
THE GEOLOGIST. 
generally of nearly five luindrcd feet, and that tlicso flowed from the peak down 
those six lateral valleys we have already mentioned. From iiis o\vii 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 who 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 delrital aeeumidations, containing large boiddcrs 
and rocks which have been brought often many hundreds 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 drift rises to very considerable heights (upwards of two thousand 
feet, and containing shells at thirteen hundred feet) above the sea in this Snow- 
donian region; and much of it, though rudely stratified, resembles ordinary 
moraine-matter. From 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 attained more than from fourteen hundred to two thousand feet, the 
formation of glaciers upon them proves the intensity of the cold at that period. 
From 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 griniliug 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 Al])ine travellers finish this 
excellent and tasteful book, which we hope will have very many readers, for 
the reason that it can neither be read Avithout interest nor wit hout profit ; and 
We are pleased to observe that a second edition is already called for. 
Map of Hereford. By T. E. Cukley, Esq., C.E. 
We gladly notice this map, sent to us a short, time since by Mr. Curley ; for, 
although a local production, and conserpicntly limited in its uses and applica- 
tion, it presents a step in a right direction, which, if followed out ni like 
manner in other districts, would render material aid to a very extended and 
minute knowledge of the stratigraphie 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 aequiruig an intimate knowledge of the rocks and soils of that 
town and its vicinity. 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 this excellent plan, and that, 
ere many years, all our towm ])lans will have as much geological information 
appended to them. The practical value of such additions cannot be over- 
estimated. 
