172 



NA rURE 



[December 24, 1891 



would rather not admit, because there is no advantage 

 gained by them and much confusion is caused, inasmuch 

 as one change often involves several others, and the 

 re-naming of large genera. According to the strict law, 

 Pimelea should be Banksia, and so Kuntze re-names the 

 latter Sinnieellera. 



It remains for botanists, who really write for the public, 

 to decide whether, in a general way, it is not better to 

 employ current names ; because it is perfectly ridiculous 

 to vapour about the " scientific " value of names. We 

 might as well attempt to purify the English language. 

 All we want is to know what plant is designated by a 

 given name, and that is no easy matter, apart from other 

 complications. 



Since the foregoing was written, I have seen an article 

 {Botanical Gaaeite, November i 891, p. 318), by Mr. E. L. 

 Rand, on " Nomenclature from the Practical Standpoint," 

 in which he recommends the course followed by the Kew 

 botanists, without any reference to them, however, or to 

 Dr. Kuntze, whose work could not have reached America 

 at that time. W. Botting Hemsley. 



APPLIED THERMODYNAMICS. 



Thermodynamics of the Steam Engine and other Heat 

 Engines. By Cecil H. Peabody, Associate Professor 

 of Steam Engineering, Massachusetts Institute of 

 Technology. (London : Macmillan and Co., 1889.) 



SUCH an important work as the present, on the inven- 

 tion which has completely changed in the course of 

 this century the conditions of human life, should not have 

 remained unnoticed so long, and an apology is due to the 

 author ; our excuse must be that the scope and power 

 of the book are such as to arrest attention and to excite 

 interest in all its various details. 



The work forms a noble companion to the " Applied 

 Mechanics" of Prof. Lanza, the author's colleague; and 

 the students of the Massachusetts Institute of Technology 

 are to be congratulated on their staff, and the possession 

 of such admirable text-books, to direct their theoretical 

 and practical studies. 



We find a great contrast here with the ordinary treatises 

 on Thermodynamics to which we are accustomed, where 

 the subject is followed up to a great extent for its mathe- 

 matical interest, and where little appeal is made to the 

 numerical illustrations on a large scale which we see 

 taking place around us ; this treatise is written much 

 more in the style of Prof. Cotterill's " Theory of the Steam 

 Engine," where the methods and results of the application 

 of Thermodynamics to engineering are developed. 



The book commences with a general theory and formal 

 presentation of Thermodynamics, as employed by the 

 majority of writers (and beyond which they rarely travel), 

 and follows the ordinary notation and treatment, but has 

 the advantage of being illustrated by carefully drawn 

 diagrams of real curves and machines, with collections 

 of instructive numerical exercises taken from real ex- 

 perience ; the student can thus test the soundness of his 

 knowledge as he proceeds. 



So long as we deal with the Theory of Perfect Gases, 

 the First Law of Thermodynamics will suffice to carry us 

 NO. 11 56, VOL. 45] 



orward ; and now the best illustrations of theory are to 

 be found in the behaviour of compressed air when used 

 as a motor — for instance, in tunnelling machinery, and in 

 the Whitehead torpedo, or in the working of Refrigerating 

 Machines (chapter xxi.), now of such importance in the 

 New Zealand dead meat trade. 



The Second Law of Thermodynamics is introduced in 

 chapter iii., as a formal statement of Carnot's principle, 

 and this again as an experimental law. Statements of 

 this law are of various kinds, but the two given here seem 

 to put the matter in as clear a light as possible : — 



(i) All reversible engines, working between the same 

 source of heat and refrigerator, have the same efficiency, 

 i.e. the efficiency is independent of the working material. 



(2) A self-acting machine cannot convey heat from one 

 body to another at a higher temperature. 



This is almost equivalent to the convention that, of two 

 bodies, the one to which heat passes by conduction or 

 radiation has the lower temperature. 



Sir W. Thomson's definition of an Absolute Scale of 

 Temperature is now deduced from Carnot's principle ; 

 and the correspondence of this scale with that given 

 practically by the air thermometer is found to be so close 

 that they may be taken as coincident. 



The theoretical advantages of Superheated Steam 

 (chapter viii.) have led inventors to repeated and costly 

 failures in their attempts at its employment, due to a 

 simple humble cause, the consequent destruction of the 

 dirty greasy film of lubricant, which keeps the working 

 parts from cutting and seizing. 



It is related that the introduction of the compound 

 principle (chapter xiii.) into marine engines was due to 

 an attempt at the employment of superheated steam, 

 and that the removal of the superheaters revealed the 

 superiority of the compound engine. 



The substance employed to do the work in a steam 

 engine is now invariably "Saturated Vapour" (chapter 

 vii.), the worst substance to choose, according to the 

 precepts of pure Thermodynamics. 



The Lawsof Saturated Vapourareempirical, anddeduced 

 from the experiments of Regnault. Here, as throughout 

 the book, the results are expressed in British units of the 

 foot and pound, while the gravitation unit of force is 

 employed, being the force of a pound in latitude 45° at 

 sea-level. 



Prof. Rowland's latest determination of the Mechanical 

 Equivalent of Heat is used, namely 427'i, in Metric 

 Units of metre-kilogrammes per calorie at i6|° C, or 778 

 foot-pounds. 



The Laws of the Flow of Fluids, investigated in 

 chapter ix., are applied immediately to the theory of 

 Giffard's beautiful invention, the Injector, in chapter x. 



Working diagrams are given of all the principal varia- 

 tions of the application of the Injector, an instrument in 

 which a jet of steam, by reason of its excess of energy 

 and momentum, is capable not only of overcoming an 

 opposing jet of water from the same boiler, but also of 

 carrying with it, in a condensed form, a much larger 

 quantity of water, and thus feeding the boiler. Still more 

 paradoxical, even the exhaust steam of an engine can be 

 made to perform the same office against a pressure several 

 fold greater. The Injector is working to the best ad- 

 vantage when feeding a boiler, as the heat of the steam 



