Notices respecting New Boohs. 393 



text-book could only impart differing degrees of prominence by-, 

 the employment of large and small types, footnotes, and other, 

 eouallv unsatisfactory devices. J. L. H. 



equally unsatisfactory devices, 



Elektricit'dt direht cms Kolile. By Etienne de Eodor. Vienna: 

 Hartleben,1897. 



The great waste which accompanies the conversion of the chemical 

 energy of coal into electrical energy, by means of the steam- or 

 gas-engine and dynamo, has led many inventors to consider the 

 possibility of directly producing electricity from cheap combustible 

 materials such as coal or carbon. The author gives an account of 

 attempts to accomplish this, classifying them according to ther 

 manner in which the carbon has been employed : thermoelectric, 

 thermomagnetic, and hydroelectric machines are thus included, as 

 well as primary batteries having a carbon electrode. J. L. H. 



Atomismus, Hylemorphismus unci Naiurwissenschaft. By Dr. A. 



Michelitsch. G-raz : Michelitsch, 1897. 

 Ueber den Urstoff unci seine Energie. I. Teil : Die iheoretische 



Becleutung cler Gesetze von Dulong-Petit unci Kopp. By Dr. H^ 



Keller. Leipsic : Teubner, 1896. 



These pamphlets both deal with the question. of the ultimate con- 

 stitution of matter. That of Dr. Michelitsch is philosophical and 

 metaphysical in character ; he seeks to show by a consideration of 

 the laws of nature that a single primary .substance {Urstoff) exists, 

 and that the various kinds of matter are merely different forms of 

 it. Matter consists of substance and form : in chemical reactions 

 substance persists, but the old form is destroyed and a new one 

 created, the substance possessing the power of assuming its form, 

 just as the power to form the fruit is contained in the seed. The 

 author objects to the atomic theory of matter on the ground that 

 it does not afford a sufficient distinction between mixture .and 

 combination,; the rearrangement of atoms during chemical com^ 

 bination merely consists in alteration of their positions in space, 

 and a similar change would take place on mechanically mixing the 

 substances. 



Dr. Keller, unlike Dr. Michelitsch, accepts the atomic hypo- 

 thesis, and finds in the law of Dulong and Petit that the atomic 

 heats of all elements are equal, an argument in favour of the 

 existence of a primary atomic substance. The atoms of all elements 

 consist of an integral number of atoms of the primary substance 

 (Uratcme), which act as centres of force, and are capable of rota* 

 tory or vibratory motion. The temperature is due to the energy 

 of vibration of these primary atoms ; the author shows, however, 

 that in gases this atomic vibration determines the velocity of trans- 

 lation of the molecule, the energies of the two kinds of motion 



