abstracts: physics and chemistry 487 



then in the transition region between a high which is retreating to the 

 eastward and a low which is advancing from the west. In cases of fall- 

 ing temperature in the free air the pressure distribution just described 

 is reversed. 



The pressure distribution in the two cases above mentioned are prac- 

 tically those which control accidental temperature changes in the air 

 which rests upon the earth's surface whence it appears that the entire 

 mass of the lower air up to at least 4000 meters, 2.5 miles is similarly 

 conditioned with respect to accidental temperature changes. That 

 accidental temperature changes such as those discussed in this paper 

 do not cease at the 4000 meter level is evidenced by the sounding balloon 

 ascensions made under the direction of the Mount Weather Observatory. 



A J. H. 



PHYSICS. — Instruments and methods used in radiometry . II. W. \Y. 

 Coblentz. Bulletin Bureau of Standards 9: 7-63. 1912. 



In this paper is given an account (see Bulletin, Bur. of Stds., Reprint 

 No. 85) of the recent development and improvement of spectral radi- 

 ation instruments. This includes air- and vacuum bolometers, thermo- 

 piles, and radiomicrometers : new combinations of instruments; linear 

 and surface thermopiles of bismuth-silver of high sensitivity ; and (Note 

 I) the Callendar radio-balance. 



The aim of the research was the production of instruments of pre- 

 cision rather than the attainment of high sensitivity. The vacuum 

 bolometer was found to excel all the other types of radiometers in 

 accuracy, in speed, and in range of sensitivity. The instrument is 

 difficult to handle and for most work the bismuth-silver thermopile is 

 recommended. The latter is as sensitive as a bolometer. The novelty 

 of this type of thermopile is the solid surface which is exposed to radia- 

 tion, thus utilizing all the energy from a spectral line, which is not pos- 

 sible with the type of iron-constantan thermopile in present use. The 

 various modifications of these thermopiles are applicable to radiation 

 pyrometers, sunshine recorders, and thermogalvanometers for measur- 

 ing weak alternating currents. W. W. C. 



CHEMISTRY. — On a modified form of stability test for smokeless powder 

 and sirnilar materials. H. C. P. Weber, Bureau of Standards. 

 Bulletin Bureau of Standards 9 : 119-129. 1912. 

 The stability test is a form of the so-called explosion test. In the 



German test the sample is heated to 135°C. and the length of time is 



