Prof. Trowbridge on the Spectra of Hydrogen. 153 



in the form of ellipses, the squares of whose axes are pro- 

 portional to the conductivity in that direction. In the 

 magnetic field the lines of force were at right angles to the plane 

 of the plate. The axes of the ellipses were measured by means 

 of the microscope. The major axis of the ellipse was, both in 

 and out of the magnetic field, at right angles to the chief 

 crystallographic axis of the crystal. The ratio of these axes, 



without magnetic field, was h =1*19, and in a magnetic field 

 of 4980 c.G.s. units A = 1*34. If we take the squares of these 



quantities we have the ratios of the heat-conductivities for 

 the two directions. The results are : — 



Zero field Jj 1*42, 



4980 c.G.s. ... Jj 1"80. 



The corresponding values for the electric conductivity are : 



Zero field ± 1-78, 



4980 c.G.s J= 1-87. 



My thanks are due to Prof. E. Warburg for his suggestions 

 throughout the progress of the work. 



Physical Institute, Berlin University, 

 Sept. 4th, 1902. 



IX. The Spectra of Hydrogen, and Reversed Lines in the 

 Spectra of Gases. By John Trowbridge *. 



IX a previous paper (Phil. Mag. July 1902) I described 

 the spectra produced by powerful condenser- discharges 

 through Greissler tubes filled with hydrogen. A fairly con- 

 tinuous spectrum was obtained between the HH lines and 

 the red end of the spectrum. This spectrum, however, was 

 traversed by reversed lines. In that paper I expressed the 

 hope of being able to obtain quartz tubes. This hope has 

 been realized. Through the kindness of manufacturers f , 

 working under the direction and according to the method of 

 Professor Shenstone J, I have obtained suitable tubes ; and 

 the results given by such tubes are so remarkable that they 

 seem worthy of a preliminary paper. 



The tubes are 8 centimetres in length, with a capillary 

 4 centimetres in length and about 2 millimetres in diameter. 

 On account of the difficulty of inserting platinum terminals 



* Communicated by the Author, 

 t Baird and Tatlock, London. 

 % Clifton College. 



