78 
THE GEOLOGIST. 
upon marine and fresli-water life, and, as might be expected, the presence of this 
substance was found to be highly injurious to it, so that the animals quitted the 
peroxide of iron as speedily as conditions would permit." 
Where these experiments ever put on record ? If so, where ? If not, can 
you tell me what was the nature of the experiments? information on this 
subject will greatly oblige, yours truly, W. P. 
REVIEWS. 
The Coal-FieUh of Great Britain : their Histori/, Structure, and Duration. With 
Notices of Coal-Yields in other parts of the world. By Edw. Hull, B.A., 
of the Geological Survey of Gr^at Britain. London: Edw. Stamford, 
Charmg Cross : 1860. 
This is a small but extremely interesting and valuable book — valuable chiefly 
liowever, for the consideration of one topic — the duration of the produce of 
our coal-fields. When we look at the fact that of the ninety-five millions of 
tons now raised for the supply of the whole world, the British Isles alone con- 
tribute seventy-five millions f and that oui' home consumption also, is not only 
enormous, but perpetually on the increase— the vital character of the question, 
in a national point of view, is strikingly apparent ; and Mr. Hull's statements, 
brief as they are, will be read with great interest even by those Avho are not 
geologists. While we have a good deal of information given us of the general 
character of the strata, physical geology, and fossils of our own, and the principal 
foreign coal-fields, in a very condensed form, all these matters are brought 
to bear upon the one important point — the exhaustion of our coal-mines. 
The results which Mr. Hull has arrived at are briefly given in his own recapitu- 
lation, and are as follows : — 1. There are coal-deposits m various parts of 
England and Wales, all at depths down to nine or ten thousand feet. 2. 
That mining is possible to a depth of four thousand feet, but beyond this the 
high temperature will prove a barrier. 3. The temperature of a coal-mine at a 
depth of four thousand feet will probably be found as high as one hundi-ed and 
twenty degrees Eahr. ; but there is reason to believe, that by the agency of an 
efficient system of ventilation, this temperature may be so reduced, at least 
during the cooler months of the year, as to allow of mining-operations without 
unusual danger to health. 4. That for working mines of greater depth than 
two thousand or two thousand five hundred feet, underground stages, with 
independent wmding machinery and engines, wiU be found not only to render 
very deep mining practicable, but also to lessen the amount of risk from accident. 
5. Lastly. Adopting a depth of four thousand feet as a limit to deep mining, 
there is stiU a quantity of coal in store in England and Wales, sufficient to 
afford a supply of sixty millions of tons for about a thousand years." 
In his summary of resources, Mr. Hull gives for England and Wales a total 
coal-containing area of three thousand seven hundred and eleven square miles 
which he considers may be worked to a depth of four thousand feet, giving thus 
a total available quantity of fifty -nine thousand one hundred and nine millions 
of tons. Takino; the present produce at sixty millions, and allowing three 
millions for the increase of future years, he considers the above supply of coal 
will last for a thousand years ; and "that for many generations to come the 
mineral resources of England are capable of bearing any drain to which they 
can possibly be subjected, either for home or foreign consumption." 
