LITERARY NOTICES. 



415 



ferent sections of the book have been as- 

 signed to educators of recognized eminence 

 and skill, especially qualified to deal with 

 the particular topics which are especially 

 given them. Thus, the sections on motion, 

 energy, force, the properties and constitu- 

 tion of matter, solids, liquids, gases, and 

 mechanics proper have been prepared by 

 Prof. S. W. Holman, of the Massachusetts 

 Institute of Technology; those on heat, 

 light, frictional and voltaic electricity, by 

 Prof. Francis E. Nipher, of Washington 

 University, St. Louis ; the chapter on sound, 

 by Prof. Alfred M. Mayer, of Stevens Insti- 

 tute ; and the sections relating to magnet- 

 ism and the practical applications of elec- 

 tricity, by Prof. F. B. Crocker, of the Co- 

 lumbia College School of Mines.. Among 

 the specific features claimed for the work 

 are the thorough and original treatment of 

 motion, energy, force, and work ; and the 

 modern and appliable conception of the 

 nature, transformation, and conservation of 

 energy, and of the relation between energy 

 and force. The book is adapted to students 

 fourteen years old and upward, but, by the 

 omission of certain classes of paragraphs, it 

 may be made comprehensible to younger 

 learners. It has been the aim of the authors 

 not to teach results merely, but to show how 

 these results have been reached, and what 

 practical use is made of them. Precedence 

 is everywhere given to the practical. 



The Evolution of Photography. By John 

 Werge. London : Piper & Carter and J. 

 Werge. Pp. 312. 



Although photography can now claim a 

 literature of its own, the historical aspect of 

 the art has naturally been neglected. Espe- 

 cially in later years has discovery followed 

 upon discovery so closely as to allow little 

 time for retrospection. The rapid introduc- 

 tion of different processes has been followed 

 by numerous treatises on special methods, 

 and manuals on the general practice of the 

 art abound, but the field of reminiscence has 

 been mostly untrodden save by Mr. Werge, 

 who in 1880 published an account of the 

 origin and process of photography. The 

 present volume easily divides itself into three 

 sections : the first containing an outline of 

 the development of photography ; the second, 

 a chronological record ; and the third, per- 



sonal recollections. The author marks four 

 periods in the history of the art : the dark 

 ages ; the age of publicity ; the epoch of 

 collodion triumphant ; the epoch of gelatin 

 successful. The dark ages include the time 

 from the thirteenth century to the advent of 

 the daguerreotype. The first three centuries 

 may be justly regarded as very nebulous in- 

 deed, without the glimmering of a photo- 

 graphic ray, and marked only by the discovery 

 of the agents that were long afterward em- 

 ployed in producing pictures. Among such 

 may be counted the invention and perfection 

 of the camera obscura and the metallic re- 

 searches of the early alchemists. The first 

 step toward acquaintance with actinic influ- 

 ence was the observation of the darkening 

 of chloride of silver in the sixteenth century. 

 As chemical knowledge increased, other 

 phenomena were noted ; and finally Scheele, 

 the Swedish chemist, experimented with the 

 prism and demonstrated the greater activity 

 of the violet ray. Meanwhile the double 

 achromatic lens had been constructed, and 

 the possibility of sun portraiture was real- 

 ized. Scientific men essayed the problem, 

 and in 1839 M. Daguerre's process was given 

 to the world by the French Academy. In 

 spite of this official announcement, there 

 seems to be every reason to agree with Mr. 

 Werge that England had preceded France in 

 photographic discovery, as the Rev. J. B. 

 Reade produced ineffaceable pictures upon 

 paper by means of tannin and hyposulphite 

 of soda in 1837. 



The next important advance was made 

 by Talbot in demonstrating the latent image 

 to be the basis of photogenic manipulation. 

 The subsequent discovery and solution of 

 gun-cotton made possible the collodion nega. 

 tives of Archer; and in 1850, a gelatin pro- 

 cess was introduced by M. Poitevin. The 

 art then enters upon its marvelous series of 

 developments ; the heliochromes of Niepce 

 de St. Victor, photo-engraving on steel, 

 orthochromatic plates, platinotypes, carbon- 

 printing, and gelatin dry plates. As a duti- 

 ful daughter of Science, Photography assists 

 in her researches, makes visible the stars, 

 the mechanism of muscular movement, and 

 the progress of disease. 



The chronological record given by Mr. 

 Werge contains not only a list of discoveries 

 and inventions pertaining to photography, 



