NATURE 



341 



THURSDAY, JULY 4, 1918. 



I'HOTOGRAPHY: PRACTICAL AND 

 THEORETICAL. 



riie Science nnd Practice of Photography :, An 

 Elementary Text-book on the Scientific Theory 

 and a Laboratory Manual. By Dr. J. R. Roe- 

 buck. Pp. xiv -I- 298. (New York and London : 

 D. Appleton and Co., 1918.) Price 2 dollars net. 



rHIS is really two books, each with its own 

 preface, though the piiging- is continuous. 

 The second part consists of the laboratory instruc- 

 tions that the author issues to his students as 

 they work through the prescribed course. These 

 instructions are not modified to render them suit- 

 able for others than those for whom they were 

 originally intended, and .so we are told that "the 

 staff reserves the right to impose fines " for break- 

 ages, that the work "confers two credits," and 

 so on. This is a trivial matter, but when we are 

 repeatedly told to consult the bulletin board, or 

 10 apply to the instructor, the difficulty is real ; 

 and, seeing that the bulletin board and the in- 

 structor are in Wisconsin, and we are in London, 

 these sources of information are impossible for us. 

 rhe course prescribed is an excellent series of 

 twenty-four experiments in the making of nega- 

 tives, printing by various processes, spectrum 

 photography, photomicrography, enlarging, the 

 use of autochrome plates, and, finally, getting the 

 •characteristic curve of a plate by means of the 

 Chapman Jones plate tester. 



The first part of the volume is of the nature of 

 an ordinary text-book, though after a few pages 

 of historical matter the author begins, perhaps 

 advisedly in dealing with students who have 

 already studied chemistry and physics, with the 

 properties of gelatine dry plates as demonstrated 

 'hy the work of Hurter and Driffield and some of 

 those who have followed them. Then icome 

 chapters on colour sensitiveness, latent image 

 theories, negative defects, positive processes, 

 lenses, the photography of colour, and a chapter 

 on "good pictures" that deals with pictorial 

 matters. There is a constant feeling in reading 

 some of these chapters that matters are mentioned 

 rather than dealt with — perhaps intentionally so, 

 seeing the circumstances in which the book 

 was originally intended to be used. Still, we think 

 that, having taken the trouble to give a diagram to 

 illustrate the production of halation and two pages 

 of text to the consideration of it, the author 

 might have explained the production of the definite 

 ring of light round a small illuminated area, which, 

 indeed, is excellently shown in some actual 

 examples given. We are told in the preface that 

 the substance of the book has been in u.se for 

 seven years, and has received innumerable addi- 

 tions and corrections. But there still remain some 

 statements that need correction or qualification. 

 J'aking the first few pages : " Toward the end of 

 the eighteenth century chlorine, bromine, and 

 iodine had all been discovered and studied " should 

 NO. 2540, VOL. lOl] 



I have "bromine and iodine " deleted, as these were 

 \ not known until 1826 and 1812 respectively. In 

 the next line, the statement that Davy and Wedg- 

 I wood "coated plates," and with, among other 

 i salts of silver, "silver bromide and silver iodide," 

 is obviously incorrect, as the results of these ex- 

 \ periments were published in 1802. On the next 

 j page we read that Daguerreotypes were fixed " by 

 i boiling in strong sodium chloride solution " until 

 t "when the solvent action of sodium hyposulphite 

 1 solution on the salts of silver was pointed out to 

 him, he changed over to it"; and a few pages 

 I further on, that French chalk is "finely divided 

 i calcium carbonate": these are examples of the 

 j statements that call for more attention. W'e thinjc 

 it a pity, too, that the author should have adopted 

 ! for his book the exact title of a text-book that has 

 I been before the public, both in this country and in 

 I America, in its various editions, for the last thirty 

 I years. 



Still, in spite of its drawbacks, there is a refresh- 



• ing originality about the volume. W^e appreciate 



to the full the author's advocacy of the importance 



; of the study of photography from both the practical 



and scientific points of view. But when he says 



that " there is no reason why the methods of 



modern science, as well as its attitude, cannot be 



taught by a course in photography, as well as by 



a course in quantitative chemistry, or in the theory 



of electricity," he doubtless means what is true, 



but will probably be misunderstood. We want the 



i chemistry, and the electricity, as well as the 



I photography, and all the other branches of science, 



for though there is a measure of overlap at every 



i division, there is no interchangeability between 



the various parts of the whole. C. J. 



TEXT-BOOKS OF CHEMISTRY. 

 \ (i) A Text-book of Inorganic Chemistry. By Prof. 

 I A. F. Holleman. Issued in Fnglish in co- 

 ; operation with H. C. Cooper. Fifth English 



edition, completely revised. Pp. viii+507. (New 

 ! York :. John Wiley and Sons, Inc. ; London : 



Chapman and Hall, Ltd., 1916.) Price 105. 6rf, 

 I net. 



j (2) Principles of Quantitative' Analysis : An Intro- 

 \ ductory Course. By Dr. W. C. Blasdalc. 

 I Second edition, revi.sed and enlarged. Pp. 

 I xii + 402. (London : Constable and Co. , Ltd., 

 ; 19 1 7) Price 105. 6d, net. 



■ (3) The Chemistry of Linseed Oil. By Dr. J. 

 I Newton Friend. Pp. vii+96. (" Chemical Monu- 

 , graphs.") (London : Gurney and Jackson, 1917.) 

 : Price 2S. 6d. net. 



THE English edition of 

 " Inorganic Chemistr\ 



Prof. Hollemann's 



widely adopted as a text-book, especially in the 

 States, that any lengthy notice of the fifth edition 

 seems almost superfluous. There are, howeve^, 

 one or two criticisms to which attention may be 

 usefully directed. It seems undesirable in a text- 

 book which is ob\iou.sly intended for more ad- 

 vanced students to devote valuable space to 

 elementary Retails flt the expense of more im- 



T 



