C. GENERiVL PHYSICS. ' 167 



curately with theoretical considerations than the results of 

 ZoUner's investigations of the same point. The principal re- 

 sults of Muller's observations were expressed by him in for- 

 mulae or curves which showed that for a given length of wire 

 of a given thickness and for a given strength of battery 

 there exists a maximum intensity of the glow; and, again, if 

 the wire of given length must be made to glow, the thick- 

 ness of the wire must lie between two well-deiined limits. 



Von Waltenhofen shows, in addition to this, that, at least 

 for the more intense stages of glow, we are always justified 

 in considering the specific resistance of the glowing wire as 

 nearly constant. Sitzh. k. Akacl. der Wisse?is., 1874, 79. 



CUEIOUS ELECTKICAL LIGHT. 



Dr. James Blake states that on the evening of the 30th 

 of September, 1874, at Placerville, El Dorado County, Cali- 

 fornia, while watching the lightning continuously flashing 

 in the southwest horizon, he observed, at a quarter past 

 seven, a luminous appearance apparently proceeding from 

 the crest of the ransce of mountains about six miles distant 

 to the southwest, which was visible through an arc horizon- 

 tally of about 15, and extended about 8 above the horizon. 

 The light lasted for about a quarter of an hour, was undoubt- 

 edly electrical, appeared like a fine display of the aurora, and 

 may have been due to the silent escape of electricity from 

 the crest of the ridge. The storm in question w^as the great- 

 est electrical disturbance recorded since the settlement of the 

 country. Proceed. Ccd. Acad, of Science^Y.^ 406. 



PHENOMENA ATTENDING ELECTRIC DISCHARGES. 



Schneebeli, in a short note on the electric discharge, ac- 

 companied wdth diagrams showing the zigzag and other pe- 

 culiarities of the discharge, states that the method which he 

 pursues for fixing these figures consists in employing a paper 

 wet upon one side with a solution of gum lac in alcohol, which 

 permeates the paper, and fixes W' ithout changing its outlines 

 the blackened trace on the other side of the paper formed by 

 the electric discharge itself. That part of the figure made 

 by the discharge which is near the positive pole is traversed 

 by very fine lines, and the isolated branches shoot from the 

 main stem in all directions. That part of the figure of the 



