NATURE 



461 



THURSDAY, AUGUST 14, 1919. 



PHOTOGRAPHY. 

 Photugraphy: Its Principles and Applications. By 



Alfred Watkins. Second edition revised'. 



Pp. xvi + 333. (London: Constable and Co., 



Ltd., 1918.) Price 105. 6d. net. 

 ^PHE Watkins exposure meter is known 

 J- wherever photography is practised, and the 

 ciany other instruments that Mr. Watkins has 

 introduced to render photography less haphazard 

 than it so often is enjoy a wide appreciation. The 

 author therefore comes to the task of writing a 

 general treatise with what we may perhaps call 

 a praiseworthy prejudice. Of this he is doubtless 

 aware, for he says in his preface: "The greater 

 attention given to my own methods in exposure 

 and development will, I am sure, be forgiven." 

 The author makes these methods clear and illus- 

 trates them well, and proves the error of certain 

 notions that have been put forward from time to 

 time, as, for example, that one should regulate 

 the exposure of the plate according to the light 

 that comes from the object rather than that which 

 falls upon it. 



As a practical guide for the ordinary photo- 

 graphy of the amateur and the professional por- 

 trait photographer, the volume deserves com- 

 mendation, although some important subjects are 

 treated of with an unsatisfying conciseness. But 

 when the author gets to matters of which he has 

 presumably not made a special study, his state- 

 ments are not so trustworthy. The confusion of 

 "focus " and "focal length " has had such distin- 

 guished and prolonged patronage that perhaps we 

 ought to pass it by ; still, it is confusion, and it is 

 avoidable. Mr. Warnerke is referred to as 

 "Warneke," and Sir Joseph Wilson Swan, who 

 ■Sied five years ago, as "Mr. J. W. Swan (now 

 Sir John Swan)." With regard to Woodbury- 

 type, we are told that "a lead mould is made of 

 a carbon print swollen in water so that the exposed 

 parts are raised," and that "in the Woodbury- 

 type process the mould was taken by placing a 

 polished sheet of lead on the wet carbon print 

 and bringing both under heav^ pressure in a 

 hydraulic press." The gelatine relief was, of 

 course, well dried before being caused to impress 

 the lead. We have said enough to mdicate that 

 some parts of the book are much in need of re- 

 vision. 



The scope of the volume, as indicated by the 

 table of contents, is very wide. We find stereo- 

 scopic work, panoramic photographs, enamels, 

 ferrotypes, night photography, animated photo- 

 graphy, "bioscope in colour," photo-telegraphy, 

 photo-surveying by balloons, kites, and aeroplanes, 

 telephotography, photomicrography. X-ray photo- 

 graphy, astronomical photography, " spectro- 

 photography, " photo-mechanical processes, colour 

 photography, etc., and each has at least an indica- 

 tion of its most obvious characteristics. 



As the results of every method of sensitometrv 

 NO. 2598, VOL. 103] 



depend upon circumstances, and there can never be 

 a standard method in a scientific sense, but only 

 by agreement for the sake of convenience, all 

 methods are of value, and we are glad to see that 

 Mr. Watkins has again brought forward his 

 "central speed " method. C, J. 



.4 RECORD OF SCIENTIFIC PROGRESS. 



British Science Guild: British Scientific Pro- 

 ducts Exhibition, Central Hall, IVestminster, 

 July 3 to August 5, 1919. Descriptive 

 Catalogue. Edited by Sir Richard Gregory. 

 Pp. xxiii + 358. (London : British Science 

 Guild, 1919.) Price 25. 6d. net. 



MERELY to enumerate the contents of this 

 interesting volume would occupy more space 

 than could be reasonably allotted to an ordinary 

 review. But this catalogue is something more 

 than a list of exhibits, even admitting that there is 

 much instruction to be derived from the descrip- 

 tions associated with the objects shown. 



The catalogue contains, first, an introduction 

 by Sir Richard Gregory, chairman of the organis- 

 ing committee, and, if read attentively, as it ought 

 to be, especially by employers and manufacturers, 

 cannot fail to have a stimulating effect. The list 

 of exhibits shows that in many directions this 

 country has regained control oi important raw 

 materials^ and by the application of scientific 

 knowledge and technical experience has achieved 

 results of which, as Sir Richard says, " the nation 

 has every reason to be proud. Now is the time to 

 see that the strong position thus gained is not 

 lost, and to unite the interests of the people of 

 these islands with those of British lands beyond 

 the seas." 



The volume before us sets out the sources from 

 which new experimental results have proceeded 

 during the war, and in the first place shows the 

 extent of the debt incurred to the scientific 

 authorities of the universities and technical 

 colleges throughout the kingdom. In despatches 

 at the end of 1916 warm acknowledgment of the 

 help thus given is expressed by Sir Douglas Haig, 

 and in 1919, again, by General Sir Henry Wil- 

 son, Chief of the Imperial General Staff. But in 

 the past manufacturers have been slow to make 

 use of the results secured by research in the 

 scientific laboratory, and it is, therefore, all the 

 more satisfactory to find that during the last five 

 years very many of them have recognised the 

 necessity of using scientific knowledge and em- 

 ploying scientifically trained men in their works 

 to a much greater extent than heretofore. The 

 result is that many industries are now associated 

 directly with research either in the separate fac- 

 tories or by a co-operative arrangement through 

 the medium of research associations. To manu- 

 facturers, whether or not they are contemplating 

 this question with a view to their own require- 

 ments, the facts and figures proAided in the 

 article on "The Organisation of Scientific Re- 

 search in Works," by Mr. \. P. M. Fleming 



B B 



