CHEWWRY AND INDUSTRY 407 REVIEWS TI1 E RARE EARTHS, TIIEIR OCCURRESCE, CJIEIUSTRY AND TECIINOLOGP. By S. I. LEVP, M A . , PIi.D., F.I.C. Sccond edition. Pp. svi-t-362. London : Edwnrd Arnold nnd Co., 1024. Pricc 18s. nct.
Thc prcscnt edition of this vnlunblc work lins bccn coinplctcly rcviscd, nnd tlic litcraturc of tlic subjcct up to June, 1024, lins bccn considcrcd in such smnll cliiingcs as hnvc bccn mncic. Tliosc sections which tlrnlt with titanium in tho enrlicr cdition linvc bccn oniittcd from tlic prcscnt edition for tlic very ndc- qiintc rcnsons that titanium is not a mcmbcr of tlic utre a r t h group, and sincc tlic first appcnrancc of this book sufliciciitly comprchcnsivc itccounts of this clcnicnt hnvc bccn publishcd clsc~vlicrc. Tho chaptcr on tlic rnclionctivity of tlic rare cnrth mincrnls hiis bccn rcwrittcn. Hcrc scctions hnro bccn includcd on tlio uranium-hcliiim, tlioriiim-hcliuni, urnniumriiditltn, urnniiuii-lend ;tnd tlioriuni-lcnd ratios, and tlic isotopcs of lciicl arc dcscribcd and cliscusscd. C h i t ciirc niid thought l i a ~o I)ccn cserciscd in tilo preparation of this edition. Dr. Lcvy has wiscly not rangcd himsclf on citlicr Hide of tlic hnfniuaiccltium controversy, and a t tlic sniiic tiinc lie lins prcscntcd tlic arguments of both aidcs impartially. ?'lint tlic dcmnnd for n book on such a spccinl siibjcct :IS tho rnrc cartlis should Inakc it ncccssary to publish it sccond edition after such a compamtircly short pcriocl is in itself n tcstimony to tlic csccllciicc of tliiit book. Tlic prcscnt edition is cqunlly csccllcnt, ;ind i t Iias carned for Dr. Lcry tlic thanks of those vngagcd in tho study of thc rim cnrtlis, for producing a book wliicli tlcnls with tlio statc of the suhjcct up to such a rcccnt dntc. J. F. SPESClslt