382 Reviews—The West Riding of Yorkshire. 
THe West Ripine or YorKSHIRE. By BreRNarD Hopson, M.Sc., 
F.G.8., xi-+ 188 pp., with 48 illustrations (not numbered), 
7 diagrams, and 2 coloured maps. Cambridge University 
Press 7 Lozi 
fete the latest addition to the well-known series of Cambridge 
County Handbooks, maintains the standard of its predecessors, 
and comprises a useful description of the natural and artificial 
features of the area under review. In the West Riding of Yorkshire 
the study of geology is of supreme importance from the commercial 
point of view, and the Coal Measures still present many unsolved 
problems of a technical character. On the theoretical side there are 
still questions of absorbing interest, as shown, for example, in a 
recent illuminating address by Professor Marr. The exact age of the 
oldest rocks of all, the Ingletonian series, is still unsettled, but there 
can be no possible doubt from their structures, lithological characters, 
and degree ‘of alteration, that they are of very early date. ‘These, 
together with the Lower Paleozoic rocks, have evidently been 
crushed up against a still more ancient mass, as so clearly shown by 
Professor Marr, and it is the nature of this ancient horst under 
the northern Pennines that provides such an interesting subject for 
speculation by theoretical geologists. Another still unsolved 
problem of a cognate character is the reason for the great change in 
thickness of the Lower Carboniferous at or near the Craven faults ; 
this also is undoubtedly tectonic in its origin, and is a striking 
example of an abrupt change of facies. Space, however, will not 
permit of a further discussion of the features of the underground or 
superficial geology of this area. In this book the author gives a clear 
account of the topography of the Riding, and its dependence on 
geological structure, and his account of the special characteristics 
of the limestone regions will be tantalizing to those not personally 
acquainted with them. 
With regard to the coloured geological map here provided, we can 
only say that it is simply deplorable, being thoroughly badly 
produced, and full of the most glaring errors. We cannot under- 
stand how the Cambridge University Press could allow such a thing 
to be issued under its auspices. 
Ore Deposition IN THE Bottvian Try-SitveR Deposits. By 
W. Myron Davy. Economic Geology, vol. xv, 1920. pp. 463-96, 
with 2 plates and 4 text-figures. 
flats author discusses previous work on the tin-silver deposits of 
the Cordillera Real and its south-eastern extension to Potosi. 
He shows that the whole of the tin mineralization was approximately 
contemporaneous and that the lodes can be divided into three types : 
(a) tin-tourmaline lodes of the high temperature zone, without silver ; 
(b) tin-silver lodes of the intermediate zones ; (c) silver lodes without 
tin. Each type is correlated with and due to igneous activity, 
