September 8, 1892] 



NATURE 



439 



tables. As they stand, a close attention to the context is 

 sometimes required in order to be quite certain of the 

 principle in which figures referred to as "calculated" 

 have been obtained. We refer chiefly to the fourth 

 chapter. There occur also, in the second chapter, some 

 terms vital to the meaning, which may require to be 

 interpreted for the benefit of the English reader; e.g. 

 Zahlenlotto, Klassenlotterie, Kontis relating to the Spar- 

 bank " Bikuben " in Kopenhagen. 



F. Y. E. 



THEORETICAL PHYSICS IN ITALY. 



Trattato di Fisico-Chimica secondo la Teoria Dinamica. 

 Opera Postuma di Enrico dal Pozzo di Mombello. 

 (Milano, 1892.) 



THIS is an elementary treatise from the hand of the 

 late Prof. Mombello, of the Free University of 

 Perugia. In the general nature of its contents it might 

 be compared to Prof. Ostwald's Allgemeine Chemie. It 

 is, however, much smaller ; and is indeed less of a sys- 

 tematic treatise than a condensed statement of the many 

 principles and laws on which physics and chemistry are 

 built. The English terms physics and chemistry have, 

 under the influence of our examination systems, become 

 so stereotyped in meaning that neither term could fitly 

 describe the character of this Trattato di Fisico-Chimica. 

 The time-honoured division of subjects would ill fit into 

 its plan. Dynamics, properties of matter, heat, light, 

 sound, electricity, and magnetism are certainly all treated 

 in their more theoretical aspects ; but there are also 

 introduced the laws of chemical combination and the 

 atomic theory, which give the book a character possessed 

 by none of our English treatises on physics. A brief 

 sketch of its character may not then be wholly valueless. 



The treatise is divided into five parts, under the head- 

 ings Dinamica, Azione Moleculare, Elettrologia, Luce e 

 Colore, Filosofia Scientifica. 



The first part contains much that we understand as 

 Dynamics ; but it contains a good deal more. In chapter 

 I. {Moto ed Energia) physics is described as the science of 

 motion. The universal law of nature is the law of 

 causality, after a brief discussion of which we are intro- 

 duced to four general principles — namely, the law of the 

 conservation of mass, the law of the equality of action 

 and reaction, the rectilinear action of force, and the com- 

 position of motions. Then follow two General Physical 

 Laws, the conservation of energy and the trans- 

 formation of energy {la correlazione ed equivalenza 

 dei moti). Thereafter are introduced somewhat less 

 general formulae, which are distinguished as Definite 

 Physical Laws and Definite Chemical Laws. Of the 

 former, two examples are given — namely, " Pascal's 

 Law " concerning the transmission of pressure in a liquid, 

 and '' Dalton's Law " that there is no physical action 

 between the particles of gases, which are not chemically 

 combinable. Then of the definite chemical laws four are 

 particularised, being distinguished by the names of 

 Lavoisier, Proust, Avogadro, and Cannizzaro, the last being 

 a modified statement of Dulong and Petit's law of the 

 specific heats of the elements. The rest of the chapter is 

 devoted to a discussion of inertia, of Newton's laws of 

 motion with special reference to the second interpretation 

 NO. 1 193, VOL. 46] 



of the third law, of kinetic {attuale) and potential energies 

 of action at a distance, and of the conception of stress 

 {confiitto) hQt^&en particles. Chapter II. {Composizione 

 dei Moti) is purely kinematical. In chapter III. {Velocita 

 moleculare) the physical molecule is led upon the stage. 

 Cohesion, viscosity, rigidity, porosity, volatility, critical 

 points, crystalline form, and gravitation — in a word, the 

 essentially molecular and dynamic qualities of bodies — 

 are touched upon ; and the whole finishes with an ele- 

 mentary treatment of the kinetic theory of gases, includ- 

 ing an account of Crookes's experiments on radiant matter. 

 It is satisfactory to notice that Prof. Mombello, like Prof. 

 Ostwald, has the boldness to speak simply of Boyle's Law 

 untainted by the Marriotte blend. This, of course, is 

 merely historic justice. On the other hand, surely 

 Herapath deserves mention as one of those who aided in 

 the development of the kinetic theory of gases. 



This early introduction of the kinetic theory has no 

 doubt its merits ; but a more logical course would have 

 been to give in the first place some notion of the real 

 meaning of temperature. This is touched upon in the 

 immediately succeeding chapter, Teoria ter mo- dinamica, 

 which forms Chapter I. of Part II. The treatment here 

 is certainly peculiar. Two theorems (enunciati), we are 

 told, are to be taken for the study of heat. The first em- 

 braces Carnot's doctrine of the logical necessity for a 

 complete cycle, and his great principle of the reversibility 

 test. Lord Kelvin's definition of temperature is brought 

 in as a kind of corollary and dismissed in a few sentences. 

 We hear no more of Carnot. " The second enunciato is 

 concerned with the fact that in the universe an immense 

 indefinite quantity of heat is being generated constantly 

 during the formation of the stars." Then follows a brief 

 sketch of some of the conclusions of spectroscopy, lead- 

 ing up to a broad discussion, in terms of the molecular 

 theory, of the meaning of temperature, and of radiant 

 energy in its four-fold aspect — thermal, luminous, chemi- 

 cal, and phosphorescent. After this thermodynamics, in 

 the usual significance of the term, is presented under 

 the guise of two propositions ascribed to Him. These 

 propositions are, to all practical intents and purposes, 

 simply the two laws of thermodynamics. But we search 

 in vain for any reference to Joule ; while Rankine and 

 Clausius are merely mentioned as having proposed a 

 demonstration of Hirn's second principle ! Now Hirn 

 deserves all credit for his experimental corroboration of 

 the truth that only a fraction of the heat which leaves the 

 boiler is transformed into useful work ; but to magnify 

 his labours in the way indicated is surely an inversion of 

 history. Moreover there is no hint as to the relation be- 

 tween Carnot's reversible engine and the second principle ; 

 and the absolute zero of temperature is defined only in 

 terms of the gaseous laws. Of entropy and the dissipa- 

 tion of energy we find no trace. 



The succeeding chapters of Part II. are devoted to 

 such subjects as the atomic theory (chemical) and the 

 various aspects of capillarity, diff"usion, osmose. Sec. A 

 brief account is also given of electro-chemistry, although 

 electrical phenomena in general are not discussed till 

 later. The seven chapters of Part III., in which elec- 

 tricity and magnetism are treated, form a highly con- 

 densed and instructive compendium of fact and theory, 

 the two not always, perhaps, very clearly distinguished^ 



