May 12, 1904] 



NA TURE 



27 



interest for general readers, and therefore is perhaps 

 wisely omitted. 



The account of the diamond takes up no less than 

 150 pages, and, large as is the amount of information 

 collected, there is much more that might with advan- 

 tage have been included if all the researches of recent 

 years could have been utilised. As it is, the book 

 brings together an enormous mass of details which 

 could only be obtained by long and patient research 

 among widely scattered sources of information. The 

 corundum and beryl gems, topaz, opal, &c. , are also 

 very fullv treated ; but an important feature of this 

 work is the account given of the large number of 

 cr\st.-illine minerals, quite unknown to lapidaries and 

 the general public, which are capable of being em- 

 ploved as gems, and as such, are scarcely, if at 

 all, inferior i:i beauty to the stones which have become 

 famous and are so universally sought after. The 

 varieties of zircon, spinel and tourmaline, which, in 

 the hands of a good lapidary, are capable of yielding 

 gems of exquisite colour and beauty, are well described 

 in this work ; while the numerous minerals which more 

 rarely yield transparent and lustrous varieties that can 

 be cut as gems are indicated by the author. In this 

 connection we may point out that even the rare and 

 beautiful varieties of spodumene — know-n as hiddenite 

 and kunzite — have been included in this edition. The 

 appendix on pearls and coral is interesting, and is 

 necessary to complete the book as a work of reference 

 on the subject. We heartily congratulate the author 

 on having found so competent and judicious a trans- 

 lator, and the translator on having devoted his atten- 

 tion to a work so well worthy of having labour spent 

 upon it 



Dr. Farrington's book is on a much smaller scale 

 than Prof. Max Bauer's, but the illustrations are of 

 the same beautiful character. The general account of 

 precious stones has to be compressed into 65 pages, 

 but, as might be expected from the author, the matter 

 is accurate and is very judiciously arranged, while 

 some of the discussions, like those on the superstitions 

 connected with precious stones, are full of interest. 

 The account of the several minerals — not only those 

 so commonly employed as gems, but the rarer ones 

 w hich can be cut and used in the same vi'ay — is, as in 

 the case of Max Bauer's treatise, very full and 

 .iccurate; but the treattnent of eacli has, from the scope 

 of the work, to be much more concise. The typo- 

 graphy and general appearance of the book are of the 

 excellence we are in the habit of finding in the best 

 publications of the .\merican Press J. W. J. 



SPECIALISED CHEMISTRY. 

 Synthetische Methodeii der organischen Chemie. By 

 Theodor Posner. Pp. xxxi + 4J5. (Leipzig: Veit 

 and Co., 1903.) 



CHEMICAL literature has assumed such enormous 

 proportions during the last two decades that it 

 i.. at times almost like seeking a needle in a haystack 

 to endeavour to find whether certain branches of the 

 subject have previously been worked at or not. The 

 diflicultv is not so much on account of the variety 

 NO. 1802, VOL. 70] 



oi books written on the different branches of chemistry, 

 although their number is colossal, but because there 

 are so many journals and periodicals, and because these 

 are so widely distributed. 



.A chemist who studies or works along a special 

 branch of the subject might hope that all others who 

 work on similar lines would endeavour to publish their 

 results in one or other of a limited number of journals. 

 -Actually this is not the case, and as a consequence he 

 must either take in an immense number of periodicals, 

 most of which time will not permit him to glance at, 

 much less study, or he must join some society which 

 takes in these journals. There is, of course, another 

 and very real objection to taking in a vast number of 

 journals — the expense. Those who devote themselves 

 to scientific research are not — generally speaking — 

 endowed with excessive riches. Chemists, therefore, 

 are ready to welcome works which are accurate com- 

 pilations of scientific research, but even here, vanitas 

 vatiitatis, the books are out of date almost before they 

 have left the press. However, they are good and 

 useful up to the time at which they were published, and 

 may save a good deal of back reference. 



The book before us is such a compilation. When 

 one is engaged on research it is of the greatest possible 

 advantage to be able to consult a work which will tell 

 us at a glance all the most important inethods for 

 carrying out this or that operation. 



For example, a chemist may be dealing with a sub- 

 stance which he suspects may be a ketone. He is 

 aware that ketones form oximes, hydrazones, semi- 

 carbazides, &c., but he may not have at his fingers' 

 ends all the methods which can be employed to bring 

 about these reactions. Dr. Posner's book will be of 

 great help to him in such circumstances. 



The book commences with a florid introduction, from 

 which we gather the author's object in writing the 

 book. It is briefly to give a collection of synthetical 

 methods which are of general applicability. Special 

 syntheses for particular compounds are not given, even . 

 when thev are of great individual importance. In 

 only giving general reactions we think the author was 

 well advised, otherwise the book must have assumed 

 unwieldy proportions. 



L'nder the heading of sulpho-acids we find various 

 methods for sulphonating the hydrocarbons, chloro- 

 ccmpounds, amido-compounds, &'C. Dr. Posner rarely 

 condescends to give e.xact methods of preparation, this, 

 we presume, because very full references are appended 

 at the bottom of each page. This is all very well 

 where one has a large library which contains the books 

 and journals from which the references are taken, but 

 it rather detracts from the value of the work. The 

 great advantage of such a work as this should be its 

 enabling one to dispense with a large number of 

 reference books. 



The book is divided into four main parts. The first 

 part deals with the hydrocarbons, and commences with 

 a short description of the different classes of hydro- 

 carbons in the aliphatic series. We then come to a 

 short description of some of the methods of preparation 

 of acetylene and diacetylene. This leads us up to ring 

 hydrocarbons and ring syntheses. Part ii. treats of 



