LITERARY NOTICES. 



501 



the good points of this intimacy, which in- 

 deed is a novel one. 



The scientific man of to-day has a large 

 and attentive audience ; and, except he be a 

 devotee to the more abstract of the sciences, 

 he is sure of immediate praise. This, too, is 

 a good result from the close connection. 

 But the effect has been, partly, to make the 

 scientist speak in a manner almost too ele- 

 mentary ; in endeavoring to make all things 

 plain, he has been obliged to hide the very 

 highest of his researches, because their dem- 

 onstration has required too great a stretch 

 of iutellect from his hearers. 



This has been, partly, inseparate from 

 the form of instruction by lectures, in which 

 form it is, of course, impossible to obtain 

 much close attention to the more complex 

 of his truths, which only allow themselves 

 to be stated in mathematical symbols. We 

 may assume the public of a scientist like 

 Tyndall or Huxley to be composed of three 

 classes : 1. Of scientists themselves, who 

 can and must consult their original memoirs, 

 and who have besides the power to supply 

 any lacunae in reasoning ; 2. Of the general 

 public; and, 3. Of a large and important 

 class of young men, students, to whom sci- 

 ence is a cultivator, and who desire didactic 

 treatises which shall give concisely and rig- 

 orously the essence of a subject, and which 

 shall not require them to consult publica- 

 tions of scientific societies, which works are 

 often beyond their reach, and to which, at 

 any rate, but few would go. 



It is, therefore, with real gratitude that 

 we must look to Prof. Maxwell for his es- 

 say on the Theory of Heat. 



It fills, exactly, a place before vacant. 

 By it we are led in a logical order, which is 

 very beautiful, from the simple idea of tem- 

 perature, through the registration of this 

 temperature, and finally to the complex idea 

 of the measure of heat. From this point an 

 analysis of the book would be almost a his- 

 tory of the development of the science. The 

 subjects of isothermals and adiabatics are 

 fully treated, and the elementary principles 

 of heat engines are stated and proved. 



While all this is done, so that a young 

 student, with due attention, may follow the 

 argument, we warn him that the book is no 

 child's play. There are no useless words 

 spent on explanations, but enough iz left to 



keep his mind clear and busy. And it \s 

 here, too, that we may speak of the admi- 

 rable manner of the book which is rigorous 

 throughout. It is an excellent preparation, 

 too, to the memoirs of Clausius, whose mathe- 

 matical essays are the acknowledged classics 

 on the subject of heat, and who still leads us 

 in the most startling way and at once to 

 differential equations, as if they were our 

 daily bread. 



We are sure that there is no one who 

 will not read Clausius " On the Steam- 

 Engine " with much greater ease for having 

 previously read this little book of 312 

 pages. The foundations of thermodynamics 

 are laid in a simple way ; and the chapters 

 on intrinsic energy, on radiation, and on 

 viscosity, are models of their kind. . 



It is, indeed, to Prof. Maxwell that we 

 owe a beautiful essay on this last subject, 

 mathematical in form, which is printed in 

 the proceedings of the Royal Society. There 

 is also in this volume a discussion of the 

 molecular constitution of bodies, which con- 

 tains much that is valuable, particularly a3 

 an introduction to the various advanced 

 essays on the same interesting topic. 



The volume is of a handy size, and is 

 fairly well printed, and there are fewer 

 blemishes in it than in any other of its 

 kind. We notice on pages 139, 152, and 

 183 (second edition), a looseness which a 

 little more care might have avoided. 



On page 139, the author, in speaking of 

 Carnot's reversible engine, says, " It is of a 

 species entirely imaginary, one which it i3 

 impossible to construct, but very easy to un- 

 derstand ; " thus putting it as a theoretical 

 device solely, as he ought. Again, on page 

 152 our author proves, or intends to prove, 

 that this engine has a greater efficiency 

 than any other engine, which he attempts 

 to do by an appeal to ordinary experience, 

 which he cites to show that no real work- 

 ing engine " can convert the entire heat 

 of its parts into work," even if this engine 

 consists in part of the theoretical Carnot 

 reversible engine. Now, he has not proved 

 this of any engine, except of those actually 

 in use, and he has expressly declared, as 

 above, that the Carnot engine cannot be 

 made : so that his proof falls to the ground. 

 And, to make matters worse, on page 183 he 

 says : " If we possessed a perfect reversible 



