Mr. J. T. Bottomley. Permanent Temperature [June 19, 



five columns are given particulars regarding the wires and the 

 current passing through them. The sixth column shows the 

 difference t 6 between the temperature assumed by the wire and 

 that of the surrounding air, the latter being in all these cases about 

 12 C. In the seventh column is given the emissivity of the outer 

 surface, or the quantity of heat (C.G.S. units) lost by the surface 

 per second per square centimetre of cooling surface per degree 

 Centigrade of difference of temperature of cooling surface and 

 surroundings. 



I may next refer to experiments on a length of wire which was 

 first tested in its ordinary state, then when highly polished, and 

 afterwards with the surface covered with coatings of shell-lac varnish 

 thickly put on and gradually increasing. 



Here I had 



Length of copper wire 50 centims. 



Diameter '97 milhm. 



Resistance with feeble current '01268 B.A.U. 



German silver wire '020 



Ratio. . . '634 

 With current of 10 amperes I found 



Condition of Ratio of 

 surface. copper to G.S. 



Bare unpolished "6635 



Bare highly polished '653-1 



One coating shell-lac '6547 



Two -6510 



Three , -6466 



Three coatings shell-lac and a covering 



of cotton wool after three minutes . . '6595 



Ditto six minutes '6668 



Ditto nine '6325 



Another wire was similarly treated with coatings of Brunswick 

 black and thin tissue paper, and gave the following results : 



Ratio of 

 copper to G.S. 



Bare wire '9895 



One coating Brunswick black '9745 



One B.B. 5-ply fine paper '9833 



One B.B. 5 paper 1 B.B "9844 



One B.B. 5 paper 2 B.B '9853 



Same with 20-ply paper added '9982 



