Intelligence and Miscellaneous Articles. 355 



selective emission of incandescent lamps with metallic filaments. 

 For tungsten the reflectivity is found to rise from 50 per cent, in 

 the yellow to 89 percent, at 2'Ojx, beyond which point it increases 

 gradually to 96 per cent, at 10 n. Mr. W. W. Coblentz also makes 

 a communication on the selective radiation from solids, in which 

 in particular a study is made of the radiation from a Welsbach 

 mantle. A remarkable difference is found between the behaviour 

 of the mantle and that of the same material when operated as a solid 

 glower heated electrically. The solid glower may emit 8*5 times 

 as much energy as the gas-mantle in order to attain the same 

 emissivity in the green. The general conclusion is that it is 

 highly probable that the radiation from the Welsbach mantle is 

 purely thermal. No. 2 also contains an account of some experi- 

 ments with coupled high-frequency circuits and some measurements 

 of electrical oscillations in receiving antennas by L. W. Austin. 



U.S. Department of Commerce and Labor. Coast and Geodetic Survey. 



Directions for Magnetic Measurements by Daniel L. Hazakd. 



Washington: Government Printing Office, 1911. 8vo, pp. 131. 

 This may be regarded as embodying the official instructions issued 

 to magnetic observers in the United States by the Government 

 Department entrusted with the magnetic survey work. The 

 volume describes the absolute magnetic instruments — magneto- 

 meters, dip circles and inductors — used by the Survey on land or 

 sea, and explains the methods of determining constants and of 

 taking and reducing observations. Instructions are given as to 

 the selection of field stations and the most favourable conditions 

 under which to observe. The Survey has several magnetic obser- 

 vatories under its control, and the volume thus naturally contains 

 a description of the magnet ographs employed and the methods 

 of standardising and tabulating the curves. At the end there are 

 D tables for use in reducing the observations and 3 giving a sum- 

 mary of regular diurnal variation results for the Survey's observa- 

 tories at Sitka, Cheltenham, Honolulu, and Porto Eico. 



XXXVI. Intelligence and Miscellaneous Articles. 



ON THE LAWS OF MOLECULAR ATTRACTION. 



To the Editors of the Philosophical Magazine. 

 Gentlemen, — 



IN a paper published in the Phil. Mag. of July Mr. Mills com- 

 pares the results of his investigations on the laws of mole- 

 cular attraction with some of those obtained by myself. The 

 paper was written when Mr. Mills had not seen some subsequent 

 papers I published on the subject, in which the relation between his 



