620 



NATURE 



[October 29, 1903 



and that ammonia, when used as a follower to 

 mercuric chloride in intensification, dissolves the silver 

 chloride and forms ammonium dimercurous chloride, 

 while sodium sulphite precipitates the mercury in the 

 metallic form. The word " sensitisers " is applied to 

 substances not usually so called, such as potassium 

 bichromate. We are told that " when toning takes 

 place with gold chloride, chlorine is given off." Of 

 course it is not " given off " as that expression is 

 commonly understood. Many other matters that need 

 correction might be noted. Generally, methods of 

 preparation are given, rather than the 'properties of 

 the things as the photographer gets them. The latter 

 is what is chiefly wanted, as photographers do not 

 make their own chemicals, nor, indeed, are the in- 

 structions herein given generally a sufficient guide to 

 enable them to do so. 



Mr. Lambert, in his two small volumes on por- 

 traiture, writes from first to last from his own 

 experience, and not only so, but in the greater number 

 of cases demonstrates by examples the effects that he 

 states result from certain procedures. The advantage 

 of colour sensitised plates can be seen at a glance in 

 the representation of the clothes, the hair, and the face 

 or complexion of the sitter by inspecting the com- 

 parative examples given. The effects of different 

 lenses, different positions of the camera, different 

 methods of lighting, variations in exposure, different 

 methods of dressing the hair and of posing the model, 

 are all demonstrated. Indeed, it Is hardly possible 

 to think of any matter that bears upon the subject that 

 is not dealt with and illustrated. The volumes are 

 very suggestive to anyone interested in portraiture, 

 and will be specially useful to the amateur who has 

 no studio at his disposal. 



Mr. Sterry has been a student of photography for 

 a great many years, and has carefully followed, and 

 often contributed to, the progress of the science that 

 has taken place during the last decade or two. He 

 is therefore specially fitted to treat of those methods 

 of photography In which reasonable methods take the 

 place of mere empiricism, and he has set down in a 

 clear manner a summary of recent work so far as it 

 affects the making of negatives and prints on bromide 

 papers, including enlargements. 



It seems to be necessary to make every book on 

 photography a kind of manual for the beginner, and 

 we suppose that Mr. Sterry has merely given way to 

 the exigencies of the case when he explains what an 

 " equivalent focus " is, and what is the size of a 

 quarter plate. However, there are not many pages 

 devoted to this sort of thing, and we judge that Mr. 

 Sterry was heartily glad when he had done with them. 

 Whatever beginners ought to do, they will not begin 

 by photographing *' by rule," and we doubt whether 

 they can advantageously do so any more than they 

 can well perform a quantitative exercise of any kind 

 before they have got an Idea as to how the action goes 

 in a merely qualitative way. We Intend it as a 

 compliment to the volume and its author when we say 

 that this book is not likely to appeal to the beginner. 



We commend the courage of the author, and 

 thoroughly agree with him when he says that hydro- 

 qulnone and ferrous oxalate are the " least desirable " 

 NO. 1774, VOL. 68] 



developers for general use. He admits, too, that 

 different results may be obtained with the same ex- 

 posures, by variations in development. Indeed, Mr. 

 Sterry treats the subject In a fair manner, and cannot 

 be accused of belonging to any particular "school." 

 We cannot endorse his statement that the light intensi- 

 ties " between deep shadow and bright sky in an 

 ordinary landscape have been conclusively shown to 

 be less than i to 32," and his reference to the proof 

 appears to be in error. The statement that the 

 principal reason why negatives for enlargement should 

 be thinner than for contact printing Is the reflection 

 of light from the surface of the paper and back to the 

 paper from the surface of the negative In the latter 

 case, Is, we think, founded on a mistaken supposition. 

 The difference appears to be due to the loss of the 

 scattered light when the sensitive surface is not In 

 direct contact with the negative. The author Is mis- 

 taken In saying that the different methods of intensifi- 

 cation give results that are " practically proportional 

 throughout the scale." But remembering that the 

 book is among the very first attempts that have been 

 made systematically to describe the new methods of 

 photography. It must be considered as notably 

 successful, though we wish It had been rather more 

 extended. " Rules " that have puzzled students for 

 years are clearly explained, and effects that appeared 

 to be erratic are shown to be the necessary results of 

 the procedure. 



OVR BOOK SHELF. 



L'Evoluhcfi cotnpar^e des Sahles. By Jules GIrard, 



Membre de la Socldtd de Geographic. Pp. Iv+124. 



(Paris : LIbralrie sclentlfique et litt^ralre, F. R. de 



Rudeval, 1903.) Price 5 francs. 

 It is not clear whether this handsomely printed volume 

 Is addressed to the geological student or to the 

 engineer. We presume, indeed, that Its production 

 has been a labour of love on the part of Its author, who 

 has brought together in a continuous form a number 

 of facts recorded in French, German, and English 

 publications. Here and there an original observation 

 Is introduced, like that on the deposit of angular 

 blocks at Vauvllle (p. 8), which appears to present a 

 problem akin to that of our Permian " breccias " on 

 the coast of Devonshire. The photographs of types 

 of sand-grains on pp. 10-13 have distinct value; in 

 Fig. 8,. however, radlolarlans, though mentioned, are, 

 to say the least, inconspicuous. 



The erosion of the earth's surface by various agents 

 is discussed, as explaining the origin of ordinary 

 sands, and stress Is properly laid on the atmospheric 

 currents as agents of transport and accumulation of 

 the fine material produced. Pp. 46-81 are, in fact, 

 occupied by the subject of blown sands and dunes, and 

 the various ways of arresting the invasion of fertile 

 areas. The horse-shoe dunes figured on p. 70 are 

 surely not so localised as the author suggests. They 

 have been well discussed by Sokol6w in a work trans- 

 lated into German in 1894, and appear, if we mistake 

 not, in the memorable pages of Sven Hedln's " Across 

 Asia." 



The description of the changes undergone by coasv 

 lines, especially in historic times, contains many 

 interesting details. We miss, however, a compre- 

 hensive summary, such as would be useful to the 

 geographer, showing how geological conditions and 

 movements of the land have affected deposition along 



