Notices respecting New Books. 469 



is a little brighter for each successive generation; but many centuries 

 must elapse before we can do much more than tell how the nearer 

 stars are situated in space." 



The contents of Part IV. relate to the stars as they are seen, 

 views of the structure of the universe, and hypotheses explanatory 

 of supposed changes in our system. 



Treatise on Photography. By W. de W. Abney, F.B.S. Longman 



and Co. 1878. 

 Instruction in Photography. By W. de "W. Abney, F.B.S. Piper 



and Carter, Grough Square, Fleet Street. 1876. 



The very rapid and continuous progress which Photography has 

 made, almost ever since the time of its discovery, a progress which 

 of late years has been one of leaps and strides, would seem to have 

 left its votaries but little time for its literature. It must be con- 

 fessed that, in this country at least, the literature of photography 

 is scanty ; and this is not a little surprising when we consider either 

 the artistic beauty of the results of photography, or its great im- 

 portance in scientific research, or even the considerable commercial 

 value of the interests involved in it. 



We hailed with great satisfaction the announcement that Messrs. 

 Longman's excellent series of Text-Books of Science was to receive 

 an addition in the shape of a Treatise on Photography by one so 

 competent for the task as Captain Abney, many of whose important 

 original contributions to the Science have enriched the pages of 

 this Journal. There is no lack of small manuals, of various degrees 

 of excellence, which give instructions for producing photographs. 

 In our experience the best of these is the small work by Captain 

 Abney whose title we have given above. Based on a set of in- 

 structions originally drawn up by him for the Photographic School at 

 Chatham, it has developed in two or three rapid editions into an 

 excellent manual, which is, in the best sense of the word, "practical." 

 It is far from being a mere compilation or transcript ; on the con- 

 trary, the instructions given, when they are not original, bear the 

 impress of being the result of a careful selection after actual ex- 

 periment. 



Captain Abney's later work fulfils a somewhat different func- 

 tion : it is designed for those who have already some knowledge of 

 photography. The earlier chapters give a brief sketch of the 

 history of the subject, which is followed by an account of the ex- 

 periments on and properties of the spectrum which directly bear 

 on photography, and an account of the changes which light pro- 

 duces on various substances submitted to its action. 



Several chapters are devoted to a detailed account of the opera- 

 tions in various processes. Both here and in other parts of the 

 work the author goes very fully into the rationale of the methods. 

 Here, however, we may note some defects, or we should rather say 

 excesses. In more than one instance the author goes beyond the 

 facts of the case. Thus the equation for the action of potassium 

 dichromate on organic matter, on page 31 , is undoubtedly incorrect, 



