Chemistry and Physics. 473 



5. Use of the Thermal Junction in the Ultra - Violet. — A. 

 Pfluger shows that it is possible to detect the heat of spectral 

 lines in the extreme ultra-violet by means of a Ruben's thermal 

 junction and the throw of a delicate galvanometer. The strong 

 lines of cadmium, zinc, aluminium, etc., gave deflections of many 

 hundred scale divisions, and even the finer lines of these metals 

 gave deflections from 20 to 100 scale divisions. 



It is shown that the energy distribution in these ultra-violet 

 lines of the metals, with the exception of magnesium and iron, is 

 strongest below wave length 260/x/x,, and in a region where the 

 ordinary photographic plate fails to register. The aluminium line 

 at 186 fifx shows a very strong energy radiation. The author 

 found it useful to use single breaks of the primary circuit and to 

 notice the first deflection of the galvanometer. The thermal 

 junction was enclosed in a vacuum to avoid currents of air. The 

 table of distribution of energy in the spark spectra of metals 

 shows that the energy of radiation of the ultra-violet lines is in 

 general far greater than the ultra-red lines. At first a quartz 

 spectrograph was used, later a Rowland grating ruled on a fluor 

 spar plate. Schumann's very short wave lengths also gave deflec- 

 tions with the thermal junction. — Ann. der Physik, No. 5, 1904, 

 pp. 890-918. j. t. 



6. Internal Friction of Nitrogen. — It is proved in the molecu- 

 lar theory of gases that the internal friction is independent of the 

 density. Prof. S. W*. Holman has shown that the dependence 

 of the viscosity upon temperature cannot be represented by a 

 function of the absolute temperature with constant exponent, but 

 that it increases the more slowly with the temperature the higher 

 this latter is. In order to retain the theory of elastic spheres, 

 Stefan imagines that the mean free wave lengths at equal pres- 

 sures increase with the temperature and the size of the molecule 

 at the same time diminishes. One cannot at present verify this 

 hypothesis by calculation. Sutherland supposes a change in the 

 attraction between the molecules is modified by a rate of collision, 

 and he arrived at a formula which expressed under this hypoth- 

 esis the ratio of the f fictional coefficients at any two tempera- 

 tures. A. Bestelmeyer takes up the measurement of the internal 

 friction of nitrogen, according to the method used by Holman 

 and arrives at the result that Sunderland's formula represents 

 with great approximation the internal friction of nitrogen between 

 300° and —190°. The departure from the law at the tempera- 

 ture of liquid air indicates the beginning of a greater friction at 

 lower temperatures. — Ann. der JPhysik, No. 5, 1904, pp. 944-995. 



J. T. 



V. Damping of Electrical Oscillations. — The resistance of 

 the electric spark assumes considerable importance in the subject 

 of wireless telegraphy. The resistance is variously extended by 

 different observers. Bjerknes estimates it at 11 ohms. Braun 

 as 0*1 ohm. K. Simons measures the amplitude of electrical 

 waves damped by spark gaps of increasing lengths, and concludes 



