380 Scientific Intelligence. 



point of hydrogen. The hydrogen thermometer can not be used 

 beyond — 194°. The helium thermometer can afford useful service 

 if it can be shown by further study to be reliable at the tempera- 

 ture — 234-5°, which is the boiling point of hydrogen. — Ann. der 

 Fhysik und Chemie, No. 9, 1896, pp. 184-92. j. t. 



5. Photometry of the ultra violet portion of the Solar Spectrum. 

 — Herman Th. Simon refers to the various methods which have 

 been employed in the less refrangible portion of the spectrum, 

 and describes an apparatus which serves for the photometric study 

 of the spectrum from the red to the ultra violet. The measure- 

 ment of light intensity with the author's method reached an 

 exactness of ^^-^ : and the qualitative determination of the ultra 

 violet absorption spectrum ol a nitrate of potash solution gave a 

 mean error of each determination of only 1 -3 per cent. 



The method consists of the use of a slotted revolving disc, by 

 means of which the light of an arc lamp is suitably weakened, in 

 order that comparison can be made with other sources of light, 

 either by the eye method or by comparison of the intensity of 

 photographic negatives. — Ann. der Physik und Chemie, No. 9, 

 1896, pp. 91-115. J. T. 



6. Electrical Indices of Refraction. — P. Drude has continued 

 his work on the electrical indices of refraction of water and 

 aqueous solutions. The method consists in measuring the varia- 

 ation in length of electrical waves along wires before and after a 

 definite length of the wires is immersed in the various solutions. 

 The results were as follows : 



For oscillations 4x10^ per second, the square of the electrical 

 index of reiraction of water for 17° C. is nb' = 81-67. 



For oscillations 1-5 X 10® per second, n^ = 80-60, for oscillations 

 8X10^ n^ = 83*6. Water shows normal dispersion within the 

 limits of the rates of oscillation. 



Between 0° and 26° changes in 71"^ are proportional to the tem- 

 perature. 



With cane sugar solutions the electrical refractive indices are 

 sensibly smaller than with pure water. The solutions show 

 anomalous electric absorption and anomalous electric dispersion, 

 and so much the more the higher the concentration. A 65-per 

 cent solution absorbs the waves like an electrolytically conducting 

 aqueous solution of the conductibility k = 3X10~\ — A?i?i. der 

 Fhysik und Chemie., No. 9, 1896, pp. 17-62. j. t. 



7. Electrical Oscillations in a condncting sphere capable of 

 polarization. — Rtdbekg, Kayser and Rtjnge have stated that 

 there exist periodic relations between the spectral lines of differ- 

 ent metals and the constitution of such metals. If N denotes 

 the period of swing of lines belonging to the same series, N =r A 

 — B n~^ — C 7i~*, in which ABC are constants, — n the position 

 number of lines in the series; ABC have different values from 

 series to series. In every spectrum there exists a principal series, 

 with easily producible and easily reversible double lines, or in 

 other words, two main series of simple lines which give oppor- 



