280 Chronicles of Science. [ April, 
and other Arctic regions during the glacial period was 7,000 feet 
thick, and that it gradually diminished in thickness towards the 
Equator. The specific gravity of the ice-sheet bemg taken to be to 
that of the earth as 1 to 7, this mass would “shift the centre 
of gravity of the earth 500 feet to the north of its former 
position, and as the ocean would accompany the centre, there 
would consequently be a submergence at the North Pole equal to 
500 feet.” Agam, “At the time that the ice-sheet would be 
forming on the northern hemisphere, a sheet of equal size would be 
melting off the southern, and this of course would double the 
effect.” This hypothesis is obviously based on the assumption 
which we have just given as the ultimate conclusion, and therefore 
rests on a most Ingenious example of the fallacy popularly known 
as “arguing in a circle.” Most of the geologists and physicists 
whose letters on the subject have appeared in the ‘ Reader,’ have 
combated Mr. Croll’s views on different grounds ; but none of them 
appear to have seen that they were endeavouring to undermine a 
house which is supported only by its roof. If an additional proof 
of the fallacy of Mr. Croll’s hypothesis be needed, it will be found 
in the fact stated in Mr. Godwin-Austen’s paper, and noticed 
subsequently in this Chronicle, that the circumpolar submergence of 
the glacial period did not extend farther southwards than a lme 
corresponding roughly with that of the Bristol Channel. 
A third volume of M. Boucher de Perthes’ now celebrated 
‘Antiquités Celtiques et Antédiluviennes’ has recently been 
published ; it contains an account of the discoveries made of late 
years in the Valley of the Somme, having reference to the 
antiquity of man, and it will doubtless be read with pleasure by 
those who take a lively interest in the questions discussed, the more 
especially as its author was the first to assert that the flint imple- 
ments of the Somme Valley-gravels were a proof that man existed 
contemporaneously with the huge extinct mammifers of the Post- 
pliocene period. 
‘Die Steinkohlen Deutschland’s und anderer Lander Europa’s, 
ihre Natur, Lagerungs-Verhaltnisse, Verbreitung, Geschichte, 
Statistik, und technische Verwendung,* von Dr. H. B. Geinitz, 
Dr. H. Fleck, and Dr. E. Hartig,’ is, as may be inferred from its 
title, a work of the most comprehensive description. The first 
volume, being the Geology, by Dr. Geinitz, has just appeared, and 
forms a valuable work of reference on the German Coal-Fields. 
In this respect it will be useful; but its value would have been 
greatly enhanced had more been said about the coal-fields of other 
countries, and less detail given about those of Germany. 
The ‘ Geological Magazine’ commenced the year with a new 
* «The Coal of Germany and other European Countries; its Nature, Stratigra- 
phical Relations, Distribution, History, Statistics, and Technical Uses,’ 
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