524 Reviews—Mineral Resowrces of Great Britain. 
secretion’. However, it was soon recognized that these theories 
left the source of the metals unexplained, and the frequent presence 
of fluorspar in large quantities was also a difficulty. In America 
many geologists appear still to hold that meteoric waters are the 
chief agent in the formation of lead-zinc deposits, especially those 
of the Mississippi valley, but in Hurope the tendency is to seek a 
deep-seated origin, and to refer the genesis of both ores and gangue 
to the intrusion of igneous magmas. In the case of the lead-zine 
veins of Cornwall, lying in slaty rocks and in obvious relation to. 
granite intrusions, this connexion may be regarded as demonstrated. 
With the ores in the Carboniferous limestone of North Wales and 
northern England, it is still a matter of speculation. 
The metaJliferous veins of the Lake District belong to a type in 
many respects intermediate between the other two. They lhe in 
Ordovician rocks, and their relations to the intrusions are obscure. 
Many of them carry a fair amount of copper, and the principal 
gangue mineral is quartz, with subordinate barytes; calcite and 
dolomite are rather uncommon, while fluorspar 1s exceedingly rare. 
A careful consideration of the facts set forth in these three memoirs 
should go far towards solving the problem, and we look forward with 
much interest to the publication of the remaining volumes dealing 
with ores of lead and zinc. The evidence thus brought together 
will also be of great value in settling another doubtful point, namely,. 
the age, or perhaps of more importance, the date of the latest phases, 
of the mineralization, which in some instances appears to have 
continued into post-Triassic times, as shown, among other cases, 
by the ores in the Dolomitic Conglomerate.in the Mendips and the 
sandstone cemented by galena at Alderley Edge. 
These publications follow exactly the plan of the other volumes of 
the series: they contain an admirably full and detailed account of 
all the mives that have been worked in their respective areas, derived 
partly from personal inspection by the authors, and when such was 
impossible, from a study of old mine plans and all other available 
sources of information. Theoretical questions are also briefly 
discussed, and it is interesting to note that Mr. Bernard Smith 
obviously inclines towards a magmatic origin for the ores of North 
Wales. The general impression gained from a perusal of these 
memoirs is that in spite of present economic conditions there may yet: 
be a future for lead and zinc mining in North Wales, if an extended 
policy of drainage tunnels can be carried out: much has already 
been done in this way, and it is devoutly to be hoped that means may 
be found to carry on and extend this work. In Cornwall, also, it 
appears probable that the deposits of lead and zinc are by no means. 
exhausted : many of the veins are also extremely rich in silver and 
may eventually again prove of considerable value. Many of the 
Lake District veins are not yet fully explored, and there are 
possibilities for barytes producuie Ds in the future. 
R. H.R: 
