Chemistry and Physics. 391 



10. The ultra red spectrum. — Professor Langley has shown that 

 the energy in the ultra red spectrum of sunlight falls off very 

 rapidly and beyond X = 5/a the energy is only measurable at certain 

 points. This remarkable fall of energy in sunlight compared 

 with that of other sources of light Langley attributes to the 

 absorption of the earth's atmosphere. H. Rubens and E. Asch- 

 kinass have studied this question of absorption by means of the 

 method used by H. Rubens in previous researches. (H. Rubens 

 and E. F. Nichols, YVied. Ann., Ix, p. 418, 1897.) This method 

 consisted in using repeated reflections from surfaces of sylvite in 

 order to obtain homogeneous rays of great wave length. These 

 rays were sent through layers of carbonic acid gas and of water 

 vapor, and it was discovered that the earth's atmosphere must be 

 non- transparent for rays of wave length 12-20/x as well as for rays 

 of wave length 24-4/x. Langley's investigations were made with 

 a rock salt prism of 3G°. This enabled him to investigate the 

 region up to 10-1 \fx. The authors state that the fact that beyond 

 the region X = 12/x the sun's rays are absorbed is of small import- 

 ance in practical meteorology since the energy of these rays is 

 small compared with that of the entire amount of emission of the 

 sun.— Wied. Ann., No. 3, 1898, 584-601. j. t. 



1 1 . Transparency of fluids for heat rays of great wave length. — 

 By means of a method of obtaining heat rays of great wave 

 length, H. Rubens and E. Aschkinass have shown that the 

 absorption of long heat rays by means of water is very great. 

 The index of refraction of water for these rays is of the same 

 order of dimension as for the visible spectrum, and the high 

 value A. = 9 obtained for Hertz vibrations must lie beyond 24/x. 

 It was found that benzol was more transparent for the long waves 

 of heat than hitherto investigated substances. Bisulphide of car- 

 bon showed a comparatively small absorption, and xylol a marked 

 transparency. The authors point out that these two substances 

 together with chloride of silver belong to that class of substances 

 for which, according to the extrapolated Cauchy formula applied 

 to infinitely long wave lengths, the square of the index of 

 refraction is approximately equal to the dielectric constant. — 



Wied. Ann., No. 3, 1898, 602-605. J. t. 



12. Electrical resistance standards. — W. Jaegee and K. Kahle 

 give a careful discussion of the results reached at the Reichsan- 

 stalt upon the tests of constancy of resistance standards. It was 

 found that the constancy of the manganine wire standards was 

 remarkable. Between January, 1895, and June, 1897, the change 

 in resistance of the standards was in the hundred thousandth 

 place.— Wied. Ann., No. 3, 1898, 456-485. j. t. 



1 3. Electric equilibrium beticeen uranium and an insulated metal 

 in its neighborhood. — Lord Kelvin with several students has 

 shown that a sheet of metallic uranium can disturb the electric 

 equilibrium in the neighborhood of an insulated metallic plate. 

 An insulated metallic plate was connected to the insulated pair 

 of quadrants of an electrometer. When the metallic uranium was 



