45 4 Scientific Intelligence. 



of dust with gaps in the scale of size, the different grades will 

 form different rings in time. — Phil. Mag., April, 1905. j. t. 



7. Spontaneous Ionization of Air in closed Vessels and its 

 Causes. — The conductivity of air and other gases is generally 

 attributed to the presence of free ions, and as these free ions are 

 continually recombining there is some agency which is splitting 

 up the combinations. Ionization in which no artificial ionization 

 agent is employed has been called spontaneous ionization. The 

 hypothesis that the ionization is due to a penetrating radiation 

 constantly passing through the atmosphere has been advanced 

 and is largely adopted. Alexander Wood of Emmanuel Col- 

 lege, Cambridge, believes from a careful inspection of indirect 

 evidence that all matter is radio-active and that the disintegration 

 processes going on in radium and the other radio-active elements 

 are going on also, though to a much smaller extent, in all matter. 

 —Phil. Mag., April, 1905. j, t. 



8. Radio-activity and Chemical Change. — N. R. Campbell 

 finds that there is no evidence that chemical change is accom- 

 panied by radio-activity ; and that the spontaneous leak increase 

 which has led some investigators to suggest such a connection is 

 due to the heating of the walls of the vessels. — Phil. Mag., April, 

 1905. j. t. 



9. Helium Tubes as Indicators of Electric Waves. — Geissler 

 tubes filled with argon, neon and other gases have been used by 

 various investigators of electric waves along wires. Ernst Dorn 

 finds that tubes filled with helium, •5-5 mm pressure are very sensi- 

 tive and do not require a dark room. — Ann. der Phys., No. 4, 

 1905, pp. 784-788. j. t. 



10. The Specific Heat of Water and the Mechanical Equiva- 

 lent of Heat. — The leading article in the Annalen der Physik, 

 No. 4, 1905, by C. Dieterici, is a careful consideration of this 

 subject, and is remarkable for the use the author makes of vessels 

 of amorphous quartz. The method adopted in determining the 

 specific heat of water was to enclose a definite quantity in a 

 quartz cylinder and after raising it to a measured temperature 

 to suddenly immerse it in a Bunsen ice calorimeter. The value 



ersr. 



419*25 X10 5 ^was obtained for the mechanical eauivalent of 



cal. 



heat.— Ann. der Phys., No. 4, 1905, pp. 593-621. j. t. 



11. Photograph of the Solar Corona loithout a Total Eclipse. 

 — In the opinion of M. J. Janssen, M. A. Hanskt has succeeded 

 in photographing the corona of* the uneclipsed sun. The results 

 were obtained at the observatory of Mt. Blanc by the use of the 

 selective absorption of different screens. The direct rays of the 

 sun were shut off by a disc. The negatives show distinct 

 halos around the disc of the sun. Photographs illustrate the 

 paper. — Comptes Eendus, No. 12, 1905, pp. 768-778. j. t. 



1 2. Kristallinische Elussigkeiten und Flussige Kristalle ; von 

 Dr. Rudolf Schenck. 159 pp., 8vo, with 86 figures in the text. 

 -—The highly important work of Lehmann on " Flussige Kristalle " 

 was published a year ago and presented a large array of interest- 



