T II E 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



OCTOBER 1873. 



XXXI. On a Relation between Heat and Static Electricity. 

 By Frederick Guthrie*. 



THE experiments to be described concern a remarkable rela- 

 tion between heat and static electricity, and may be briefly 

 described as exhibiting (1) the difference in power which one and 

 the same body at different temperatures possesses of discharging 

 electricity of one kind, and (2) the difference in power which 

 one and the same body at the same temperature has of dischar- 

 ging the two kinds of electricity. 



A great many of my experiments involved the use of white- 

 or red-hot metal balls. Those I used were the ordinary cast-iron 

 balls about two inches in diameter, provided with eyes. An 

 insulating handle was made by fastening a stout copper wire hook 

 by means of thinner wire to the end of an ebonite pen-holder 

 about six inches long. When no insulation was required an ordi- 

 nary iron hook was used. The iron balls were heated in a clear 

 coke fire. Each experiment was made never less than twelve, 

 and mostly from twenty to thirty times, on different days. The 

 two gold-leaf electroscopes which I used kept their charge with- 

 out sensible loss for from five to ten minutes. 



§ 1. Experiment. — A white-hot iron ball being hooked out of 

 the fire by the insulating hook and brought into contact with the 

 -f conductor of an electrical machine, and then brought near to 

 or touching the top of an electroscope, produces no divergence of 



* Communicated by the Author. (An abstract of this investigation 

 appears in the ' Proceedings of the Royal Society,' February 13, 1873 : 

 vol. xxi. p. 168.) 



Phil. Mag. S. 4. Vol. 45. No. 306. Oct. 1873. T 



