Chemistry and Physics. 577 



paper also contains a discussion of the nature of positive ions in 

 different gases, when the ionization has settled into a steady 

 state. — Phil. Mag., Oct., 1908, pp. 657-691. J. t. 



8. Amount of Radium, Emanation in the Atmosphere near 

 the Earth's Surface. — Experiments on this subject have been car- 

 ried out by Professor Eve at McGill University, Montreal, in 

 a room fifty feet above the ground. The outside air was 

 drawn through cotton wool ; then through three glass tubes con- 

 taining cocoanut-shell charcoal. The air currents were continued 

 for 2*7 days, at a speed of 6*7 cm 3 /sec. The tubes were then 

 heated over Bunsen burners, so that the gases absorbed by the 

 charcoal were expelled and collected over water and then exam- 

 ined in the usual way, by means of an electroscope. It was 

 found that the amount of radium which would be in equilibrium 

 with the average amount of radium emanation in a cubic meter 

 of air at Montreal measured at intervals 1907-8 is 60 X 10 -12 gram. 

 This amount varied with cyclonic and anticyclonic conditions — 

 but not appreciably from summer to winter. — Phil. Mag., Oct., 

 1908, pp. 622-632. J. T. 



9. Absorption of Rontgen Rays. — Dr. Adams, working in the 

 Jefferson Physical Laboratory, measured the absorption of these 

 rays through various substances (this Journal, xxiii, Feb., 1907; 

 also Proc. Am. Acad., xlii, No. 26). W. Seitz, in a preliminary 

 paper, undertakes the same subject with the modification of using 

 an aluminium window in the X-ray tube, to diminish as much as 

 possible the sifting of the rays due to glass walls. — Ann. der 

 Physik., No. 12, 1908, pp. 301-310. j. t. 



10. The Zeeman Effect in Solar Vortices. — The announcement 

 of the discovery of this effect by Professor Geoege A. Hale of 

 Mt. Wilson Observatory has led to interesting discussions in 

 Nature, Oct. 8 and Oct. 29, 1908. j. t. 



1 1. The Study of Stellar Evolution, an Account of some Recent 

 Methods of Astrophysical Research ; by George E. Hale. Pp. 

 xi + 252, with 104 plates. Chicago, 1908. Decennial Publications 

 of the University of Chicago, Second Series, Yol. X. — The study 

 of solar physics is a territory which resembles Central Africa, — 

 many men have visited it and have picked up treasures here and 

 there, but almost no systematic attempt has been made until the 

 last few years to unravel its mysteries and to introduce order into 

 the chaos of isolated facts and theories which have been gathered 

 in the general store of knowledge. As is generally known, Pro- 

 fessor Hale has embarked on such a venture at Kenwood, at the 

 Yerkes Observatory, and for the last three years at Mount Wilson 

 under the auspices of the Carnegie Institution. With a multi- 

 tude of problems under investigation, it is too early yet to expect 

 very extensive results : the facts have still to be obtained. 



The volume under review may be classed as a sort of travel- 

 ler's guide, showing the roads which have already been opened, 

 the methods used for continuing the exploration and the theories 

 which indicate directions for future work. Its plan is best de- 



