98 



NATURE 



[December i, 1892 



that Victor Meyer now seals up bulbs of oxygen and hydro- 

 gen (electrolytic gas) in a similar way, and that these, like 

 their confreres of CI and H, can be kept not only in the 

 dark for any time, but, unlike these, also in the light with- 

 out undergoing any change. "The fact that many gases 

 when perfectly dry do not combine is illustrated by the 

 case of chlorine and metals — brass and sodium, pp. 84 

 and 85 — as well as of carbon monoxide and oxygen, for 

 these gases will not explode if dry, p. 189. A more striking 

 way of illustrating this latter case than that with the 

 eudiometer is not mentioned. I will add it. Dry a 

 current of carbonic oxide over glass balls moistened with 

 strong sulphuric acid ; light the stream of gas issuing from 

 a horizontal tube ; then plunge over the blue flame a 

 cylinder full of air which has been previously dried by 

 shaking it up with a little strong sulphuric acid. The 

 flame instantly goes out. Another case of the kind ob- 

 served by Arnold lends itself to a lecture experiment. He 

 found that powdered iron will not burn in pure dry oxy- 

 gen, and in order to be able to estimate hydrogen in iron 

 it was found necessary to insert a small tube containing a 

 drop of water, through which the oxygen passed before 

 coming into contact with the iron, this tube being of 

 course weighed both before and after the experiment. 

 This may well be included in the next edition, which I 

 hope will soon be called for. Another capital experiment 

 to show that iron can be carbonized by contact with a 

 diamond was recently described to me by Mr. Gilbert 

 Fowler, of Owens. A loop of pure thin iron wire is placed 

 in a vertical glass tube surrounded by an atmosphere^f 

 hydrogen. Below the loop is a splinter diamond (or 

 some diamond dust) placed on the top of .a glass rod 

 working through the lower end of the tube. After heat- 

 ing the wire by a current to the highest possible tempe- 

 rature without fusion, bring the diamond carefully into 

 contact with the heated iron. The metal at once fuses. 

 But of good experiments "there is no end" (Mr. Newth 

 describes 620 for the non-metals alone) whilst of a review 

 of a book in Nature there must be a speedy end, and I 

 will end by advising all those who like to see and to show 

 good experiments to get Mr. Newth's book. 



H. E. RoscoE. 



A MANUAL OF PHOTOGRAPHY. 



A Manual of Photography. By A. Brothers, F.R.A.S. 

 (London : Charles Griffin and Co., 1892.) 



MR. BROTHERS has in this well-illustrated book 

 brought together a great amount of information 

 relative to the history, processes, apparatus, materials, 

 &c., which will be welcomed by all who are interested, 

 even if only in a general way, in the fascinating art of 

 photography. The work covers about 360 pages, is 

 divided into five parts and is accompanied by a full 

 index. 



In the short historical sketch which is introduced as 

 the opening chapter, the author by means of quotations 

 and otherwise gain much information which is not readily 

 accessible, and many facts that are not inserted in our 

 treatises, and which consequently are not generally 

 known. At the present day, when so many possess a 

 NO. 1205, VOL. 47] 



camera of some sort or other, it is very curious to carry- 

 ourselves back to the time of Daguerre and to picture 

 to ourselves the idea which he put forward when he 

 wrote in his pamphlet, "Those persons are deceived 

 who suppose that during a journey they may avail 

 themselves of brief intervals while the carriage slowly 

 mounts a hill to take views of a country." Whether this 

 is or is not the case now we will not stop to discuss, but 

 we may mention that many other very interesting ex- 

 tracts are made from the same source. 



The next three chapters deal with the chemistry, 

 optics, and light as applied to photography. In these 

 there seems to be nothing that calls for special attention, 

 unless it be to state that the author has written them in 

 a charming manner, as for instance the short sum- 

 mary under the heading " Magnesium Light," which 

 one reads with quite renewed interest. 



Coming now to Part II., Processes, we find the 

 most important section of the whole book. As Mr. 

 Brothers rightly observes, the old processes pre- 

 vious to the introduction of the gelatine bromide 

 methods have been put completely in the shade, 

 not because they have been surpassed by better and 

 more trustworthy ones, but simply because they require 

 a little more care in manipulation and consequently the 

 consumption of more time. In order to remedy this ta 

 some extent he has given great prominence to them, de- 

 devoting nearly 140 pages to them, including working- 

 details of the more important later processes. For the 

 sake of facility of reference they are arranged in 

 alphabetical order, and in many cases they are ac- 

 companied by illustrations which show the actual 

 results that can be obtained by the uses of the methods 

 under consideration. To cite them in anything like 

 detail would carry us too far away, but we may men- 

 tion one or two briefly. The (wet) collodion process 

 is of course here fully described : the author lays special 

 stress on the advantage of this process, for there is no 

 doubt that where dry plates are now used far better 

 results could be obtained by employing this old wet 

 process. The photo-mechanical process, collotype^ 

 receives also a rather lengthy description, but its utility 

 and the excellence of the results obtained necessarily 

 give it some prominence. A specimen illustration of 

 the last mentioned is inserted, as well as one of a 

 recent application of this method for printing in colour^ 

 Printing on wood, photo-lithography, platinotype, &c., 

 together with photogravine Woodbury type and a host 

 of others, are all described, some briefly, others of greater 

 importance somewhat more in full. 



Parts III. and IV. deal with the apparatus and 

 materials used in the production of a finished picture. 

 In the former the author describes the particular 

 characteristics of many of the various kinds of cameras 

 and accessories, while in the latter are explained the 

 chief uses and actions of the chemicals employed. 



Part v., the last, contains short notices of the applica- 

 tions to which photography has given rise. Astro- 

 nomical Photography is referred to at some length, 

 and we may mention that we have an excellent 

 reproduction of one of Mr. Rutherfurd's beautiful lunar 

 photographs taken at first quarter. The practical 



