:oo 



NATURE 



\Nov. 29, I 



Bermudas, which are more than three times the distance 

 from the nearest mainland, will give some idea of the 

 differences in the age of the two. The latter contains no 

 endemic genus, and only about half a dozen species, and 

 these are not of a highly differentiated character — one is 

 a portion of a very old flora, and the other a flora of 

 recent derivation. The small flora of Juan Fernandez 

 (which lies about 400 miles from the coast of Chili) con- 

 tains 21 per cent, of endemic genera and 78 per cent, of 

 endemic species. 



The endemic element in Socotra is distributed over 

 fifty-four natural orders, and includes some highly curious 

 types, such as Cocculus Balfourii, remarkable for its thick 

 rigid cladodes and often leafless condition ; Thamnostna 

 socotrana, a member of a Mexican genus ; Dirachma, 

 a geraniaceous genus of American affinities ; Dendrosicyos, 

 unique in the Cucurbitaceae for its arboreous character ; 

 Trichocalyx, a new genus of the Acanthace^e ; Cockbiirfiia, 

 a new genus of the almost exclusively African Selagineae ; 

 and Cculocarpiis, a new genus of the Verbenacese, having 

 strong American affinities. Of the 136 genera to which 

 the endemic species belong, 98 are only known to be 

 represented by endemic species ; and of the 20 endemic 

 genera, 18 aremonotypic. The isolated types of American 

 affinities are a repetition of what has also been observed 

 in the fauna and flora of Madagascar. 



In summing up. Dr. Balfour finds that the affinities of 

 the flora are essentially tropical African and Asian, the 

 former more pronounced. A former, though very ancient, 

 land connection with Africa he regards as conclusively 

 proved, and the evidence strongly favours the supposition 

 that it was also united with Arabia. With regard to the 

 element of strongest American affinity, its presence is 

 still an unsolvable problem. W. B. H. 



THE METALLURGY OF GOLD. 

 The Metallurgy of Gold ; a Practical Treatise on the 



Metallurgical Treatment of Gold-bearing Ores. By M. 



Eissler. (London : Crosby Lockwood and Son, 1888.) 

 'T^HE title suggests that this little volume is a more 

 -i- comprehensive treatise than the author has at- 

 tempted to write, but it is nevertheless likely to be useful 

 to a large class of readers. 



There is a wide-spread belief that, as much of the gold 

 in Nature is found in the "native" or metallic state, its 

 metallurgy must be comparatively simple ; and so it would 

 be in nearly all cases if it were not for the fact that the 

 precious metal often occurs in a very fine state of division, 

 or in association with sulphides and tellurides of other 

 metals. Ignorance as to the true nature of such ores has 

 led to their being considered to be " base " or " rebellious,'' 

 and has entailed much loss and disappointment. 



It is asserted, on p. 5, that native gold is never quite 

 pure, being almost invariably alloyed with silver ; refer- 

 ence might, however, have been made to the interesting 

 deposit of gold of exceptional purity recently discovered 

 at Mount Morgan, in Australia. 



The author points out that " the loss on working gold 

 ores, even with our most modern appliances, is still enor- 

 mous"; and he gives, among other statistical statements, 

 the results of seven years' working in Colorado, where 

 the average value of the precious metal in the ore, by 



assay, was ^7 \%s. per ton, while the amount actually ex- 

 tracted was only ^3^ showing a loss of over 60 per cent. A 

 large section of the work is devoted to the consideration 

 of methods of concentrating the free gold lost during 

 crushing and amalgamating, and the processes for ex- 

 tracting the gold either by amalgamation or by chlorin- 

 ation. The author writes with a practical experience 

 of the processes he describes, but his information is in 

 many cases not up to date. 



The illustrations are usually very clear, but in no 

 instance is the scale on which they are drawn given, 

 and there are too few references to the dimensions of the 

 appliances described. The appearance of the illustra- 

 tions often suggests that they have been borrowed from 

 the trade circulars of the makers of mining machinery. 

 It would surely have been possible to give a more 

 intelligible section of a chlorination works than the one 

 (p. 142) which was suitable enough for its purpose when 

 it originally appeared as an incidental illustration to an 

 Ofiicial Report to the United States Government pub- 

 lished in 1873 ; and a far more useful drawing might have 

 been found to accompany the description of the refining 

 of gold by Miller's process than the diagrammatic one 

 which was drawn eighteen years ago by the v/riter of the 

 present review in order to make the nature of the 

 process clear in an Official Memorandum, 



More useful information than is to be found in the 

 twenty-one pages devoted to assaying might easily have 

 been condensed into them, and it is much to be regretted 

 that no attempt has been made to deal with the treat- 

 ment of tellurides, which are so troublesome to the 

 smelter, and have occasioned so much loss. In a future 

 edition it would also be well to give a description of the 

 process of collecting the precious metals in lead, whicli 

 plays so important a part in the smelting of complex 

 auriferous ores of lead and copper. Hydraulic mining, 

 also, should find a place. Certain defects of style will 

 no doubt be corrected in a second edition ; this will be 

 welcome, for, although the work is hardly in sufficient 

 detail to justify its being called a "practical treatise," it 

 will be useful, especially to men who are engaged in 

 smelting. The author suggests that it contains sufficiently 

 full information for " investors and others interested in 

 gold-mining operations who may wish to gain an intelli- 

 gent insight into the modus opera7idi at the gold-mines.'' 

 To them it may be warmly recommended, for, although 

 the element of speculation can hardly be separated from 

 genuine investment in gold-mines, the " adventurers," to 

 use the old name, often deliberately neglect all investi- 

 gation into the nature of the methods by which they 

 hope to profit. W. C. Roberts- Austen. 



OUR BOOK SHELF. 



Viaggio di L. Fea ifi Birmania e regioni vicini. II. 



" Primo saggio sui Ragni Birmani." Del Prof. T. 



Thorell. (Genova : Tipographia del R. Istituto Sordo- 



Muti, 1887.) 

 Dr. Thorell deserves our best thanks for having begun 

 a faunistic work on the spiders of Burmah ; still greater 

 would have been our gratitude had his minute and ex- 

 haustive descriptions been accompanied by figures of 

 the numerous new species recorded. One of the great- 

 est hindrances in the study of exotic araneology is the 

 paucity of such works. The present, however, is not 



