REVIEWS. 
THe Pratinum Metars. By A. D. Lumps. Imperial Institute 
Monographs, pp. ix + 63, with 1 map. London: Murray. 
1920. Price 3s. 6d. net. 
eee publication forms one of the useful series of monographs on 
metals issued by the Mineral Resources Committee of the 
Imperial Institute. It comprises a full account of the world’s 
resources, so far as known, of the metals platinum, palladium, 
iridium, osmium, ruthenium, and rhodium. Owing to the disturbed 
state of. Russia and the collapse of the platinum supply, much 
prospecting has been carried out in other lands, but without great 
success. The author of this monograph has evidently followed up 
with great care all recent available information on the subject, and 
has produced a very complete account of the present state of our 
knowledge. Dupare’s great work was, of course, not published 
when he wrote, but he has compiled a very good account of the 
platinum deposits of the Urals. Incidentally, we are pleased to see 
that Russian names are correctly transliterated, instead of the 
irritating germanized and gallicized versions that are commonly 
current in geological literature. To British geologists some of the 
most interesting occurrences of platinum are those found in 
association with the nickeliferous sulphides of Sudbury, Insiswa, 
and elsewhere. In 1918 Ontario produced nearly 5,000 troy ounces ; 
this seems to occur as sperrylite, which is the only known native 
compound of platinum. 
On p. 38, near the middle, we do not think that the author really 
means that the country rock largely consists of olivenite. This some- 
what hypercritical remark may be permitted, since we have found 
the work very free from errors. 
A Series or Nets ror THE ConsTRUCTION OF MODELS ILLUSTRATIVE 
OF THE SIMPLE CRYSTALLINE Forms. By James B. JorRDAN. 
London: Thomas Murby & Co. 1921. Price 3s. net. 
Ne access to a set of suitable models is essentia! for the study of 
crystallography, and as models in wood are somewhat 
expensive, it is often helpful for the student to make use of card- 
board models which he can easily construct for himself with the 
aid of nets, i.e. outlined drawings of the crystal faces, printed on 
paper or cardboard, and so arranged that they can be cut out and 
folded up to represent the form required. 
A set of 41 nets originally drawn and published some fifty years 
ago by Mr. James B. Jordan, has recently been re-issued by Messrs. 
Murby & Co. This re-issue is welcome, and most of the nets will still 
be found useful, but in the interval which has elapsed since they 
first appeared, crystallography has made notable advances, and 
