148 Scientific Intelligence. 



8. Deductive Physics ; by Frederick J. Rogers, M.S. Large 

 8vo, pp. vi, 260. Ithaca, 1897 (Andrus & Church).— " The 

 object of this volume," the author tells us in the preface, u is to 

 present in compact, though logically complete form, the principal 

 facts, laws, definitions and formulas of the science of physics." 

 Unquestionably the two errors to which text-books are most liable 

 are bulkiness with corresponding diffuseness, on the one hand, and 

 compactness with more or less unintelligibility, on the other. To 

 select the right mean between these undesirable extremes is often 

 a difficult matter. The book before us is certainly compact ; but 

 as a text-book it seems to us dry. Supplemented, however, as it 

 is intended to be, with experimental lectures, it will, no doubt, 

 serve a good purpose as a compendium of facts and principles for 

 ready reference. It is provided with numerous problems and is 

 well illustrated with diagrams. g. f. b. 



9. Modes of Motion y or Mechanical Conceptions of Physical 

 Phenomena ; by A. E. Dolbear, Professor of Physics, Tufts Col- 

 lege. 16mo, pp. iv, 119. Boston, 1897 (Lee & Shepard). — 

 A series of discussions to show the close relationships of physical 

 quantities and their nature as modes of motion. 



10. Electrical Wind. — It is still an open question whether it is 

 possible to electrify air which is entirely free from dust particles. 

 Late investigations by Lord Kelvin tend to prove that air can be 

 electrified. S. Arkhenitts describes experiments which support 

 the view that the so-called electrical wind or electrical point r 

 working, is due to an electrification of the surrounding medium 

 by means of which the molecules are separated into ions which 

 then manifest their electrical charges and repel one another. An 

 arrangement with fine points which could be electrified was sus- 

 pended by a torsion wire in a suitable vessel which could be 

 filled with dry air, hydrogen, oxygen and marsh gas. The 

 reaction of the suspended apparatus was found to be proportional 

 to the gas density, and the experiments therefore support the 

 electrical ion theory rather than the dust theory. — Wied. Ann., 

 lxiii, 1897, pp. 305-313. 



The results of Arrhenius appear to be contrary to those 

 obtained by E. Warburg,* who finds by the use of an electro- 

 meter that dry air freed Irom dust cannot be electrified and that 

 the bearers ot electrical charges in moist air are drops of water. 



J. T. 



1 1. Heat produced by the Rontgen rays. — E. Dorn believes that 

 he has detected an effect of heat produced by the Rontgen rays. 

 The method employed to detect the heating was that described 

 by Toepler for the measurement of very small pressures (Wied. 

 Ann., lvi, p. 609, 1895). Two connecting vessels are in communi- 

 cation with a tube containing a column of light, easily moving 

 fluid-like toluol. One vessel is screened from the effect of the 

 X-rays, while the other, which contains a strip of metal, is exposed 

 to their action. A change in the pressure-level was detected and 



* Wied. Ann., lxiii, 1897, pp. 411-418. 



