98 



NATURE 



[November 30, 1899 



out his deductions. There is but one thing lacking, and 

 that is the devotion of any special chapter to those 

 diseases of the ear — notably the condition known as 

 middle ear sclerosis — acknowledged to be hereditary, or 

 to the diseases of the throat and nose which are pre- 

 disposing causes of deficient hearing power. Considering 

 the large percentage of all forms of nasal obstruction 

 existing in the condition of civilisation — a percentage 

 larger, we believe, in America than in Europe — it would 

 be of interest to investigate the influences diseases of the 

 throat and nose exercise upon the marriages of persons 

 suffering therefrom. 



In spite of the fact that statistics are always somewhat 

 dry, and the deductions given from those in Mr. Fay's 

 work are put without useless verbiage, the book is a very 

 readable one to those interested in all branches of the 

 subject, and should rank high as a work of reference. 



MACLEOD YE.^RSLEY. 



THE LIQUEFACTION OF GASES. 

 The Rise and Development of the Liquefaction of 



Gases. By Willett L. Hardin, Ph.D. Pp. viii + 250. 



(New York : The Macmillan Co. London : Mac- 



niillan and Co., Ltd., 1899.) 

 La Liquefaction des Gaz et ses Applications. By Prof. 



Julien Lefevre. Pp. 175. (Paris : Gauthier-Villars et 



Fils, and Masson et Cie.) 



A BOOK should be criticised with reference to the 

 author's professed object in writing it. Dr. Hardin 

 professes to have written for the popular reader, in the 

 popular science style. Regarded from this point of view 

 the work deserves a good deal of praise. It is, in the 

 first place, interesting to read, collecting, as it does, a 

 great many facts connected with the development of low- 

 temperature research, and detailing numerous experi- 

 ments which are explained with the assistance of copious 

 and clear illustrations. It may therefore be recom- 

 mended, with the reservations which are made below, to 

 those who, with a very elementary knowledge of physics, 

 desire to learn something of the details of recent progress 

 in a very interesting subject. The recommendation 

 should be all the heartier because the author's style is 

 free from the patriotic brag and boom which disfigure 

 another recent American book on the same subject, and 

 because the right side is taken as to the marvellous 

 industrial revolutions heralded from America as a con- 

 sequence of later work in this department of science. A 

 further merit in the work is the abundance of exact 

 references to original authorities, for the benefit, as 

 stated in the preface, of those who wish for fuller in- 

 formation. 



The fact, however, that the author had the latter object 

 in view emphasises what should be a binding obligation 

 even in books intended solely for popular reading, 

 namely, to take care that such science as is introduced 

 shall be strictly correct ; and this obligation Dr. Hardin 

 has fallen short of in a serious degree. On pp. 183-185 

 he reproduces Edwin J. Houston's suggestions for an 

 apparatus to produce intense refrigeration. The nearest 

 thing to a novelty in these suggestions is the proposal 

 to modify Windhausen's machine by substituting a two- 

 NO. 1570, VOL. 61] 



stage compressor for a single-stage one, and so obtain- 

 ing a higher pressure of sixty atmospheres. He expressly 

 retains Windhausen's system of power expansion in a 

 cylinder doing work on a piston ; yet Dr. Hardin says : 



" In the apparatus suggested, Houston anticipated the 

 methods which were employed twenty years later in the 

 liquefaction of air by Linde, Hampson and Tripler." 



This is inexcusable in one who undertakes to " enable 

 the popular reader to understand the principles involved.'^ 

 The same confusion is repeated much more deliberately 

 later on. On pp. 205-208 the author works out mathe- 

 matically the formula for the cooling produced by power , 



expansion, ( — ) =™) which he calls equation (7). 



P\ Tj 



He then says : 



"Applying these results to the liquefaction of gases by 

 means of the regenerative coil, it is evident that the ex- 

 pansion of the gas in the tube lowers the temperature by 

 an amount which corresponds to equation (7)." 



The formula for power expansion is here applied where 

 we ought to have had Thomson's formula for free ex- 

 pansion, - '^ = A (?Z37\ • The title of the section 



dp ^ t / 



is "Theory of the Self-intensification Method of Re- 

 frigeration," and a note, at the foot of the same page, 

 refers us to Joule and Thomson for a more complete 

 discussion, which, however, in the body of the section, 

 instead of being abridged or summarised, is altogether 

 replaced by another analysis. The way in which the 

 book is written gives no reason to suppose that Dr. 

 Hardin is incapable of distinguishing between the very, 

 different conditions involved in power-expansion and 

 free expansion, or the very different mathematical 

 analyses appropriate to these two sets of conditions. 

 The only tolerable explanation of such a gross confusion 

 is that it has never come in Dr. Hard4n's way to read 

 Thomson's papers on the cooling of gases by free ex- 

 pansion, or to examine intimately the nature of the 

 phenomena involved, and so he has carelessly applied to 

 these phenomena the well-known formula for cooling by 

 power-expansion. This is not the proper way to write a 

 book even for the satisfaction of the interest of the 

 popular reader. These are not the only instances that 

 the author shows of a lack of thorough acquaintance 

 with his subject. If he had studied Mr. Tripler's British 

 patent of 1893, which is put forth as the foundation of 

 his claims as inventor of a form of self-intensive air- 

 liquefier, and had paid attention to the chronology of 

 the subject, Dr. Hardin would perhaps not have felt 

 justified in treating those claims so well as he has done, 

 by describing those parts of Mr. Tripler's apparatus 

 which are not kept secret. On p. 227, the author gives 

 Prof. Dewai-'s conclusion, that the liquefying points of 

 hydrogen and helium are near together, without giving 

 the subsequent correction. 



The style of the writing is occasionally careless and 

 slipshod, and the meaning sometimes undiscoverable. 

 On p. 209 we are told 



" the issuing jet experiences a much greater decrease in 

 temperature owing to the greater difference between the 

 initial and final pressures." 



