194 



NATURE 



[June 28, 1900 



The rocks which have brought Christmas Island into 

 the most prominent notice are the thick beds of nearly 

 pure lime phosphate capping several of the higher hills. 

 It is inferred that this deposit has been formed by the 

 action of beds of guano on limestone forming the summits 

 of the low islets presumed to have existed previous to 

 the first elevation of the present island. Another phos- 

 phatic bed is considered to have been produced by 

 guano acting on volcanic ash. It is for the purpose of 

 working these phosphates that the island has been leased 

 by a commercial company. 



Although the greater part of the volume is of a highly 

 technical nature, it must not be inferred that this is the 

 case with the whole of its contents. As an example of 

 its lighter side, the excellent account of the habits of the 

 Frigate-bird may be cited. These birds, which form 

 the main support of the present colony of the island, are 

 of an inquiring and fearless disposition. 



"The usual way of obtaining them is," writes the 

 author, " for a man to climb into the topmost branches 

 of a high tree near the coast, armed with a pole eight 

 or ten feet long and a red handkerchief. The latter he 

 waves about, at the same time yelling as loudly as 

 possible. The birds, attracted by the noise and the red 

 colour, swoop round in large numbers, when they are 

 knocked down with the long pole. In this way suffi- 

 cient birds to supply the small colony with food can 

 usually be obtained in an hour or two ; occasionally, 

 however, in unfavourable states of the wind, they are 

 difficult to procure." 



From first to last, the exploring, the collecting, and 

 the descriptive and literary portions of the book have been 

 thoroughly well carried out. And, despite the fact that 

 no far-reaching or epoch-making discoveries, in either 

 zoology, geology, or distribution have been made, all 

 concerned in the production of the volume before us 

 (save the printer) are to be heartily congratulated on 

 the manner in which they have executed their respective 

 tasks. R. L. 



A NEW WORK ON SILVER. 

 Metallurgy of Lead and Silver. Part ii. Silver. By 

 Henry F. Collins. Pp. 352. (London : Griffin and 

 Co., Ltd., 1900.) 



WE recently had occasion to notice the first volume 

 of the present work, and to speak favourably of 

 its merits. We are pleased to find the second portion 

 equally good. It has been a source of great regret that 

 the distinguished master of metallurgy, the late Dr. 

 Percy, did not live to complete his projected work on 

 Silver, instead of leaving what has been termed a splendid 

 fragment : and as no book claiming to give a full account 

 of the metallurgy of the subject has been published since, 

 we cordially welcome the advent of a further contribu- 

 tion. It is perhaps unnecessary to point out how closely 

 interwoven is the metallurgy of lead with that of silver, 

 or to state that a full treatise on silver cannot be written 

 without considerable reference to lead ; and when 

 one author is competent to deal with both branches of 

 the subject, it affords the best means of imparting a 

 sound knowledge of these metals. In the present case 

 we have this additional advantage, that the editor ig an 

 NO. 1600, VOL. 62] 



authority on all questions relating to the nature and pro- 

 perties of silver, together with that of assaying. The 

 immense importance of silver in the economic relations 

 of the United States is well known, and many attempts 

 have been made to introduce similar relations into this 

 and other countries ; hence it may be considered one of 

 the most important metals known to mankind. The 

 present work is not an exhaustive treatise on silver, and 

 is evidently intended chiefly for those who are connected 

 with the extraction of the metal from its ores. Those 

 ancient methods which are fast becoming obsolete have 

 not escaped notice ; for, while they may not possess 

 much practical. value at the present time, their chemical 

 and educational value is not to be despised. Numerous 

 references to original sources of information are given 

 throughout the volume, and this will enable the reader to 

 obtain fuller information than is given here. The method 

 of procedure in special works, such as that of matte 

 smelting at Sunny Corner (p. 268), is described at some 

 length with clearness and precision. The author has 

 followed the same plan as in his first volume, of econo- 

 mising space by giving details of the practice at 

 different localities in the form of tabular statements. 

 This should prove useful for reference and comparison. 

 The book is divided into four main sections, dealing re- 

 spectively with silver and itsores, amalgamation, lixiviation. 

 and smelting processes. Of these the chapters relating to 

 lixiviation and blast furnace smelting are the best^ 

 as they appear to be the branches with which the author 

 is most familiar. The hyposulphite leaching process is 

 described in a more lucid and methodical manner than 

 we have seen elsewhere, and the advantages and dis- 

 advantages of calcium sulphide are admirably compared 

 on p. 197. A chapter is specially devoted to hypo- 

 sulphite leaching practice, in which is given details of 

 plant, mode of working, advantages and disadvantages 

 of lixiviation, cost, and examples of the Russell process 

 in various localities. Data as to cost and results at 

 mills using the Patera and Russell processes respectively 

 are given in the form of tables on pp. 224 to 227. A 

 serviceable chapter on the refining of lixiviation sulphides 

 concludes the section. The fourth section, dealing with 

 the extraction of silver by smelting processes, contains a 

 considerable amount of information in a condensed form. 

 The table of comparison of various systems of smelting 

 is instructive and helpful. The construction of furnaces 

 is made clear by the aid of figures, drawn to scale. The 

 arguments in favour of the hot blast for smelting mattes 

 are pertinent and convincing. Several well-compiled 

 tables are included in this chapter. Pyritic smelting 

 receives only a brief notice in Chapter xv., as this sub- 

 ject has been partly dealt with in the first volume. The 

 subject of matte smelting in reverberatories for silver- 

 copper ores is next considered, and the characteristics 

 of the method, with the points of difference from blast 

 furnace practice, are pointed out. This kind of information 

 is often of great moment to the practical man, who has 

 to decide on the most economic method to adopt in 

 special cases. The final chapters deal with the treat- 

 ment of argentiferous mattes, which generally require a 

 preliminary concentration to eliminate some of the lead 

 and iron. In some cases a direct method may be 



