v mt 
Reviews—Fluorspar. 479 
upon the Armorican movements, which produced folding, faulting, 
cleavage, shearing, and jointing. The most important cross-faults 
give evidence of lateral movement. The Pleistocene accumulations 
consist of the well-known raised beach, cave-deposits, and glacial 
accumulations. The raised beach is regarded by Dewey as inter- 
glacial, and the existence of glacial deposits older than the beach 
is “ slightly suggested at two places ” in this area. The relations of 
the beach to the cave-deposits with Pleistocene mammals “ do not 
appear to have been established beyond doubt ” Glacial deposits 
newer than the raised beach consist of gravels and loamy and gravelly 
boulder-clay. 
The latest formations are river-terraces, a submerged forest, 
alluvium, blown sand, and shingle beaches. Much light has been 
thrown on the organisms and human artefacts of the submerged 
forest group by the labours cf A. L. Leach. 
A brief chapter on economics closes the memoir, though, as stated 
in the Director’s preface, “few deposits of economic importance 
occur within the boundaries ”’ of the district. Notwithstanding this, 
the work recorded in this and the previous memoirs of the area 
around the South Wales Coalfield, especially those parts referring 
to tectonics, will no doubt be of the utmost utility in helping to 
solve economic problems in the future. These memoirs, indeed, 
are an admirable illustration of the value of the work of the Survey 
in aiding economic geology indirectly as well as directly. We feel 
confident that Dr. Flett’s hope ‘‘ that this district will be recognized 
by students and teachers of geology as a typical area for the study 
of the formations represented, as developed in the south-west of 
Wales,” will be fulfilled, and are glad to note that he calls attention 
to the fact that copies of the 6 in. maps “ may be seen at the offices 
of the Survey, where also the fossils collected may be examined ”. 
Students and teachers, and, indeed, all other geologists, may be 
congratulated that a district so interesting alike for its physiography 
and its geology is elucidated by so excellent a memoir. Mr. Dixon 
has produced a work of bigh merit, well got up, well illustrated, and 
at a price that compares favourably with that of some of the memoirs 
of the latter part of the last century. 
ds As Ml 
Fiuorspar (1913-1919). Imperial Mineral Resources Bureau 
Digests. pp. 18. 1921. Price 9d. 
[ROOST has always been a favourite mineral with collectors, 
mainly on account of the variety and beauty of the specimens 
obtainable. Its origin also presents problems of much interest to 
the petrologist and student of ore-deposits. Of late years it has also 
become of considerable technical importance, as a flux in the making 
of steel by the basic open-hearth process, in the preparation of 
electrolytes used in the reduction of aluminium ores, and for 
