146 



NA TURE 



[December iS, 1902 



volumes in which the theory of explosion motors and the 

 nature of the combustibles used therein are detailed in 

 a thoroughly clear and systematic manner. The two 

 volumes cover to a certain extent identical ground, but 

 in the earlier work the subject is treated in its widest 

 sense and the mechanical features of the motor vehicle 

 as a whole are freely investigated ; while in the later 

 work the author confines himself exclusively ' to the 

 engine, and here brings the theory of the subject well 

 into line with the latest developments in practice, at 

 the same time indicating the directions in which further 

 improvements may be arrived at. 



In the earlier work, the opening chapter is devoted to 

 purely theoretical considerations of motors operating with 

 perfect gases, and the laws regulating the behaviour of 

 such gases under varying conditions of pressure and 

 temperature. The imperfections of the gases actually 

 available in practice are then considered, and the working 

 conditions of the various cycles which may be employed 

 are investigated. A chapter is devoted to the question 

 of the specific heats of gases under various conditions, 

 the question of the rate of the explosion relative to piston 

 velocity, and the losses in actual engines due to throttling 

 at the inlet and exhaust, to the cooling of the cylinder 

 walls and to heat rejected on exhaust ; representative 

 diagrams are given and the total losses discussed. 



Three chapters are then devoted to questions connected 

 with the mechanical design of engines and motor vehicles, 

 such points as the movements of the piston, connecting 

 rod and crank-pin, valve movements, frictional losses 

 and the strength of materials being fully discussed. 

 All the chief organs of the transmission gear and 

 special items such as axles, wheels, brakes, pneumatic 

 tyres, carburettors and ignition apparatus are dealt with 

 in detail, the author carrying his investigations in this 

 portion of the work far beyond the limits indicated by its 

 title. The nature and properties of the various com- 

 bustibles which are available for explosion motors are 

 next fully considered, the author remarking with much 

 truth on the extraordinary ignorance amongst constructors 

 on this particular branch of the subject. The work con- 

 cludes with a comparison of trials of motors and auto- 

 mobiles, and considerations relative to the most suitable 

 cycle to employ, the author advocating a six-stroke cycle 

 namely, admission, compression, expansion, recompres- 

 sion, explosion, exhaust — the advantages gained being a 

 better mixture, re-heating of the charge after it has en- 

 tered the cylinder, and abstraction of heat from the 

 walls, which would diminish the loss to the cooling 

 water. 



In the more recent volume, which is based on a series 

 of lectures delivered before the Automobile Club of 

 France, the functions of every type of explosion engine 

 which may be employed on a motor vehicle are in- 

 vestigated in a systematic manner. All the most im- 

 portant points in the design of engines, such as the 

 volume of the compression chamber relative to the total 

 cylinder volume, the influence of the walls, of the periods 

 of admission and exhaust, and of the propagation of the 

 explosion are carefully considered. 



The concluding chapter, which forms nearly one-third 

 of the volume, is devoted to the nature of the combustibles 

 which may be employed, to the best conditions for the 

 NO. 1729, VOL. 67] 



running of an engine and to investigations of the inertia 

 of the reciprocating parts. 



The subject in both volumes is handled in the clearest 

 possible manner, and although higher mathematics is 

 freely employed in every investigation, each step is so 

 carefully traced that the author may be followed to his 

 conclusions by all who possess a practical knowledge of 

 the subject of explosion engines. 



C. R. D'Esterre. 



MARIGNAC AND HIS WORK. 

 CEuvres computes de Jean-Charles Galissard de Marign ic. 

 By E. Ador. Tome i., 1S40-1860. Pp. lv + 701. 

 (Geneve : Eggimann, n.d.) 



THIS edition of the works of Marignac is prefaced by 

 a biographical sketch by his son-in-law, Prof. Ador. 

 From this sketch, we learn that Marignac, a native of 

 Geneva, came of a scientific stock ; at the house of his 

 uncle, Le Royer, he early made the acquaintance of 

 distinguished men, of whom there has been no lack in 

 his native town. Prevost, De Candolle and Dumas 

 were frequent guests in Le Royer's pharmacy, and from 

 them young Marignac imbibed that single-hearted devo- 

 tion to science which so strongly characterised him. He 

 began his career, not as a chemist, but as an engineer ; 

 he was a pupil of the Fcole Polytechnique, and later of 

 the Ecole des Mines, at Paris. His talents had so 

 strongly impressed the French authorities, however, that 

 long after he had ceased to be connected with France 

 and had accepted his chair at Geneva, the French 

 Government expressly granted to him the right to keep 

 the title " Ingenieur des Mines," in spite of his having 

 ceased to be a French subject. 



In 1S40, when twenty-three years of age, he came 

 under the magnetic attraction of Liebig and passed a 

 semester at Giessen ; and it bears high testimony to 

 Marignac's genius to find that after that short probation 

 he was offered, and accepted, the much-coveted post of 

 chemist to the porcelain factory at Sevres. He occupied 

 the position only six months, and on receiving a call to 

 fill the chair of chemistry in the Academy of Geneva (for 

 the University had not at that time been created), he at 

 once accepted, finding his life work in an academic career. 

 As professor there, he lived and died, although in 187S 

 he withdrew from active teaching. Never robust, he 

 succumbed gradually to an insidious disease, and he 

 died in 1894, after a long and tedious illness, borne with 

 the utmost fortitude. His lectures were models of 

 method and clearness — indeed, these were the charac- 

 teristic features of all his work — and his modesty, 

 patience and perfect conscientiousness gained for him 

 the esteem of the whole scientific world, testified by the 

 numerous honours which fell to his lot. 



His only researches in the domain of organic chemistry, 

 no doubt suggested while in Liebig's laboratory, dealt 

 with phthalic acid and the action of nitric acid on 

 naphthalene. It was at Geneva that he began the series 

 of investigations on atomic weights which have rendered 

 his name famous. The inducement was to test Prout's 

 law ; and the ratio between the atomic weights of 

 chlorine, potassium and silver first occupied his attention. 

 His attempts to prepare pure material for experiment 



