13 



THE POPULAR SCIENCE MONTHLY. 



loss of one fifth in efficiency they are on an 

 equality with locomatives at sixty miles an 

 hour ; below that speed the locomotive is to 

 be preferred ; beyond it, the motor is the 

 cheaper servant. 



While this work shows evidence on every 

 page of the scientific mastery of its subject, 

 the authors are plainly men desirous of meet- 

 ing the practical difficulties which the opera- 

 tion of electric railways presents every day. 

 They are also fully aware that the investor 

 is less interested in the analysis of electrical 

 machinery than in the simple question, Will 

 it pay ? Commercial considerations receive 

 full and sensible treatment. Others than 

 superintendents and investors can read this 

 work with profit. It is as good an example 

 as American literature contains of scientific 

 principles applied to the solution of practical 

 problems problems, too, as important in 

 their social as in their commercial bearings. 

 Progress in electric traction means the relief 

 of congested cities, the expansion of whole- 

 some suburbs, on a scale impossible to the 

 steam locomotive. In long-distance service 

 it stands for an advance second only to that 

 due to George Stephenson. 



Scientific Correspondence of Joseph 

 Priestley. Edited, with Copious Notes, 

 by Henry Carrington Bolton. New 

 York : privately printed. Pp. 240. 

 Price, $2.50. E. F. Brown, 180 Warren 

 Street, Brooklyn, Agent. 



The " Father of Pneumatic Chemistry " 

 expected to be remembered chiefly for the 

 theological views which he put forth, having 

 been in early life a Unitarian minister, and a 

 writer on theological subjects throughout his 

 career. Hence his modest autobiography, 

 which was expanded into two volumes, with 

 the addition of several hundred letters, by 

 his son and J. T. Rutt, contains almost noth- 

 ing about his scientific investigations. To 

 supply the lack of material relating to his 

 work in the latter field, Dr. Bolton has col- 

 lected ninety-seven letters, nearly all written 

 by Priestley, his correspondents being Josiah 

 Wedgwood, Captain James Keir, Sir Joseph 

 Banks, and others in England, and Dr. Ben- 

 jamin Rush and others in America after he 

 came to this country. They contain many 

 interesting details concerning the progress of 

 his researches on the gases, several of the 

 most important of which were discovered by 



him. The letters are supplemented by many 

 biographical, bibliographical, and explana- 

 tory notes by the editor, and the volume con- 

 tains a portrait of Priestley and one of Jo- 

 siah Wedgwood. There is also a synopsis 

 of correspondence of Dr. Priestley, consist- 

 ing chiefly of letters from him to his brother- 

 in-law, Mr. Wilkinson, from 1790 to 1802. 

 An appendix contains a descriptive list of 

 the likenesses of Joseph Priestley in oil, ink, 

 marble, and metal, embracing ninety-three 

 items ; an account of the Lunar Society, in 

 Birmingham, founded by Matthew Boulton, 

 Erasmus Darwin, and others, and of which 

 Priestley was a member ; and an inventory 

 of Dr. Priestley's laboratory, which was 

 sacked by rioters in 1791. 



Diphtheria: its Natural History and Pre- 

 tention. By R. Thorne Thorne, F. R. S. 

 London and New York : Macmillan & Co. 

 Pp. 266. Price, $2. 



Statistics show that the death-rate from 

 diphtheria in England and Wales has been 

 increasing during the last twenty years, and 

 more rapidly in the cities than in the coun- 

 try. This disease thus presents a contrast 

 to the majority of zymotic diseases, the death- 

 rate from which has been lessened as physi- 

 cians have gained more knowledge of their 

 nature and as sanitary conditions have been 

 improved. In view of its fatal and little un- 

 derstood character, the author has under- 

 taken to collect what is known in regard to 

 diphtheria. It appears that the broad geo- 

 logical features of a district have no influ- 

 ence on the development or diffusion of the 

 disease. A chart prepared by Dr. G. B. 

 Longstaff shows that the death-rate has been 

 high in some counties and low in others on 

 the same geological formation. Yet the au- 

 thor is convinced that a surface soil which 

 retains wetness and organic refuse, together 

 with an aspect exposed to cold wet winds, 

 tend to the fatality of diphtheria. He fur- 

 ther discusses' the general nature of the dis- 

 ease, its relation to scarlet fever and to croup, 

 the influence of schools in spreading the in- 

 fection, and milk as a vehicle in which it may 

 be carried. The measures of prevention 

 which are suggested by his study of the sub- 

 ject are stated in detail, and his general con- 

 clusions as to the natural history of diph- 

 theria are also given. The volume contains 



