﻿Chemistry and Physics. 481 



8. Fluorescence. — M. Lecoq de Boisbaudran calls attention to 

 the fluorescence manilested by various salts of manganese under 

 the influence of electrical discharges in vacuum tubes. The 

 fluorescence of certain of these compounds provides an extraordi- 

 nary sensitive reaction to detect the presence of manganese in 

 substances which give no trace of it by ordinary reactions. Sul- 

 phate of lime and carbonate of lime mixed with very small pro- 

 portions of manganese render, after strong calcination, magnificent 

 fluorescence. — (Jomptes JRendus, No. 10, Sept. 6, 1886. j. t. 



9. Instantaneous Photography. — M Maeet has devised an 

 arrangement by means of which the light coming from the back- 

 ground against which the quickly moving objects are photo- 

 graphed can be cut off. This light has hitherto affected the sensi- 

 tive plates and often injured the clearness of the impression. By 

 means of certain precautions, M. Marey has been able to reduce 

 the time of pose, for each image, to '002 of a second and hopes to 

 still further reduce it. The new photographs show an extraordi- 

 nary clearness of impression under the shortening of the time of 

 exposure. The pivoting of the wings of birds upon their longi- 

 tudinal axis is clearly shown and also other and various peculiari- 

 ties of their flight. The author expresses his obligation to certain 

 suggestions of Chevreul. — Comptes Hendus, No. 13, Sept. 27, 

 1886. j. t. 



10. A Potential strengthener for measurements. — All electro- 

 meters hitherto constructed do not equal galvanometers in sensi- 

 tiveness and accuracy of indication. Hallwachs has invented 

 a species of induction machine which can be used in connection 

 with a quadrant electrometer. His paper gives a careful descrip- 

 tion of the apparatus and a discussion of the errors to which it is 

 subject. This apparatus consists of a half cylinder condenser, of 

 which the collector can be set in rotation and thus be placed 

 opposite, and in turn removed from the condensed plate. The 

 instrument gives for one Daniell cell with a scale distance of 3 

 meters 300 scale divisions on changing the quadrants of the 

 electrometer. — Ann. der Physik und Chemie, No. 10, 1886, pp. 

 300-313. j. T. 



11. Compressibility and Surface Tension of Liquids. — W. C. 

 Rontgen and J. Schneider are occupied upon a research in this 

 subject with various chemically well defined substances. Their 

 present paper is a preliminary one. Among its results, however, 

 is the following : If the fluids examined are arranged in the order 

 of compressibility, the. following order is observed: J, No 3 , Br, 

 CI, OH, S0 4 , C0 3 , H, Am, Li, K, Na. The authors discuss the 

 order of compressibility of various salts of the above, for in- 

 stance, LiN0 3 , NaN0 3 , etc., and find that the compressibility 

 of a salt solution is smaller than the arithmetic mean of the 

 compressibility of an equally concentrated solution of salt and 

 of base. — Ann. der Physik und Chemie, No. 10, 1886, pp. 

 165-213. j. t. 



12. Observations on pure Ice and Snow. — Some experiments 

 have been made by T. Andrews in regard to the relative conduc- 



