1877*] T 7 z<? Great Ice Age and Origin of the “Till” 
215 
an advantage even over Norway in being much better known 
in geological detail. Besides this, we must always permit 
the expounder of any subjedt to seledt his own typical illus- 
trations, and welcome his ability to find them in a region 
which be himself has diredtly explored. 
Mr. Geikie’s connection with the Geological Survey of 
Scotland has afforded him special facilities for making good 
use of Scottish typical material, and he has turned these 
opportunities to such excellent account that no student 
after reading “ The Great Ice Age ” will find fault with its 
decided nationality. 
The leading feature — the basis, in fadt — of this work de- 
serves especial notice, as it gives it a peculiar and timely 
value of its own. This feature is that the subjedt — as com- 
pared with its usual treatment by other leading writers — is 
turned round and presented, so to speak, bottom upwards. 
De Saussure, Charpentier, Agassiz, Humboldt, Forbes, 
Hopkins, Whewell, Stark, Tyndall, &c., have studied the 
living glaciers, and upon the data thus obtained have iden- 
tified the work of extindt glaciers. Chronologically speaking 
they have proceeded backwards, a method absolutely neces- 
sary in the early stages of the enquiry, and which has 
yielded admirable results. Geikie, in the work before us, 
proceeds exadtly in the opposite order. Availing himself of 
the means of identifying glacial deposits which the retro- 
gressive method affords, he plunges at once to the lowest 
and oldest of these deposits, which he presents the most 
prominently, and then works upwards and onwards to recent 
glaciation. 
The best illustration I can offer of the timely advantage 
of this reversed treatment is (with due apology for neces- 
sary egotism) to state my own case. In 1841, when the 
“ glacial hypothesis,” as it was then called, was in its 
infancy, Prof. Jamieson, although very old and nearly at 
the end of his career, took up this subject with' great enthu- 
siasm, and devoted to it a rather disproportionate number 
of lectures during his course on Natural History. Like 
many of his pupils I became infedted by his enthusiasm, and 
went from Edinburgh to Switzerland, where I had the good 
fortune to find Agassiz and his merry men at the “ Hotel des 
N eufchatelois ” — two tents raised upon a magnificent boulder 
floating on the upper part of the Aar glacier. After a short 
but very adtive sojourn there I “ did,” not without physical 
danger, many other glaciers in Switzerland and the Tyrol, 
and afterwards pradtically studied the subjedt in Norway, 
North Wales, and, wherever else an opportunity offered ; 
