REVIEWS 707 



deep interest in physiology, which greatly adds to the value of the work as a text- 

 book for students. If it is true that the volume does not contain one or two things 

 that perhaps it might, it is also true that it contains many valuable things which 

 are not to be found elsewhere. 



A. D. Darbishire. 



The Mechanical Production of Cold. By J. A. Ewing, C.B., LL.D., F.R.S., 



M.Inst.C.E. [Pp. x. + 204, 71 illustrations.] (Cambridge University 

 Press, ioi'.) 



This book is, in the main, a reprint of the " Howard " lectures delivered by 

 Dr. Ewing before the Society of Arts in 1897, but a good deal of matter has been 

 added and a few corrections made. As the additional matter is chiefly in the 

 direction of explaining the applications of refrigeration and the corrections very, 

 very few and unimportant, we realise, even if the author had not indicated to us, 

 that " in its main features the art of refrigeration has undergone little change " in 

 the eleven years that have elapsed since the lectures were delivered, and yet what 

 a vast field the subject offers for research ! 



The original form of lectures has been retained, and so, instead of chapters, we 

 have six lectures which occupy the first 180 pages, the remaining 20 pages being 

 devoted to six appendices. 



Lecture I. deals with the general principles of refrigeration, and, some small 

 knowledge of thermodynamics being assumed, the "efficiency," or more correctly 

 the " coefficient of performance " of an apparatus for the production of cold, is 

 discussed, it being explained that the term " production of cold " simply meaning 

 the reduction of the temperature of a body below the general level of temperature 

 of its surroundings, and the apparatus employed a "heat pump" or refrigerating 

 machine — the various types of which are described in outline to be dealt with in 

 detail in subsequent lectures. 



On page 2 we find : " The commercial importance of mechanical refrigeration is 

 indicated by the fact that there are two journals exclusively devoted to the subject — 

 the American Ice and Refrigeration and the German Zeitschrift fiir die gesammie 

 Kalte-Industrie." In keeping with the rest of the volume, a footnote should have 

 been added indicating that the number has now greatly increased, and in England 

 alone we have two important journals, of which Ice and Cold Storage should 

 certainly not be overlooked. 



Lecture II. deals very thoroughly with air-machines, Lecture III. with absorp- 

 tion-machines, and Lecture IV. with the vapour-compression process — ammonia, 

 carbonic acid, and sulphurous acid machines. Very important practical and 

 theoretical comparisons are made between the various types of machines in the 

 latter lecture ; and we find on page 86: "The convenient range of pressure of 

 ammonia and the comparatively small bulk of the machine commend it to general 

 acceptance . . . there can be no question that, whatever the merits of other types, 

 the Fammonia-compression machine stands easily first as regards the ratio of 

 refrigerating effect to power expended in producing it." 



Throughout the first four lectures the importance of the range oj temperature 

 in estimating the coefficient of performance is kept constantly to the front, and it 

 was, perhaps, hardly to be expected that the author would have added to his work 

 of 1897 by suggesting values for T, and T 2 which could be used as a standard 

 range for estimating the performances of refrigerating machines, and yet such a 

 means of rating is one of the wants of this branch of engineering. 



Trials of refrigerating machines and the uses of mechanical refrigeration are 



