REVIEWS. 
67 
with which we have long been familiar, they are, as a whole, not only 
well drawn, hut also judiciously selected for the purposes of illustration. 
There is throughout this work evidence of much patient compilation, and 
it undoubtedly contains a considerable amount of useful information. It is, 
however, to be regretted that sufficient care has not been exercised in the 
exclusion of error, and that when generalization has been attempted it 
becomes obvious that the author does not possess a sufficient grasp of the 
subjects of which he treats. 
A list of such inaccuracies would exceed the limits of our space, but a 
few only of those which have been observed may be cited as examples. 
It is stated (p. 79) that ‘ all the gold-bearing rocks lie below the Car- 
boniferous group,’ whereas it is well known that the majority of the rocks of 
the gold regions of California are Jurassic. 
We are informed (p. 1 13) that ‘ the presence of silver in lodes or strata 
is not observed in beds newer than the Cambrian limestone.’ All who 
possess a competent acquaintance with such subjects are, however, aware that 
the Great Comstock Lode of Nevada, which since its discovery some twenty 
years ago, has produced silver to the value of 40,000,000/. is enclosed within 
walls of undoubted Tertiary age, and that the vein itself is probably not older 
than the Pliocene period. 
With regard to lead ore it is stated (p„ 236) that its highest horizon ‘is 
found in the Carboniferous Limestone, this horizon being divisible into two 
zones ; one in the pale-coloured massive limestones near the base of the 
series, and the other in the limestones and grits near the summit.’ The 
annual production of 40,000 tons of lead ore from the Bunter sandstone 
of the Diiren and Commern districts in Germany is certainly a somewhat 
remarkable exception to this generalization. 
We are taught (p. 280) that ‘the geological horizon of the ores of 
mercury ranges from the summit of the Lower Cambrian rocks to the base 
of the Llandeilo beds of the Cambro-Silurian strata.’ Is Mr. Davies aware 
that the highly productive quicksilver mine of New Almaden in California, 
and several others in that country, occur in rocks of Cretaceous age F 
Turning from the distribution of metalliferous minerals to the statistics 
of their production, we still find inaccuracies, but space permits us to mention 
only two of them. At p. 121 the annual production of copper in Spain is 
stated to be about 6000 tons, whereas two Spanish mines alone produced 
above 20,000 tons of that metal during the year 1877. Again (p. 197) 
the annual production of lead in Belgium is estimated at 700 tons ; reliable 
statistics show that the production of that country in 1876 amounted to no 
less than 6973 tons of metallic lead. 
It will be seen from the following observations on the rocks of Cornwall, 
that many of the opinions brought forward differ materially from those 
accepted by geologists. At p. 128 when speaking of these rocks the author 
states : — In maps they are all included as Devonian, which is, I think, 
•with all deference to other observers, a mistake. My own interpretation 
of the ages of the strata I have just described is this: — The granitic 
masses belong to the Laurentian or the base of the Cambrian, the hornblende 
slates with the serpentine, and porphyries, to the Cambro-Silurian, the 
