DISCHARGE OF ELECTRICITY FROM HOT PLATINUM. 
247 
the oas molecules, and tliat below a certain in'essnre the leak iri air dimiiiislies with 
the joressure unless the P.L). nsed is too small to produce ions by collisions.'"' 
In the following paj^er the residts are given ol experiments on the variation ol the 
leak from hot platinum wires witli the temperature of tlie wire, the pressure ol the 
gas, and the nature of the gas. Some results are also given on the leak from a hot 
palladium wire. The rest of the paper is divided into the following sections : 
(1.) Description of apparatus, fee. 
(2.) Tlie leak in air, nitrogen and water vapour. 
(3.) The variation of the negative leak with the temperature. 
(4.) The leak in hydrogen. 
(5.) The leak from palladium in hydrogen. 
(G.) Summary of principal results. 
(7.) Conclusion. 
(I.) Description of Appamtns, dn. 
The apparatus used is shown in fig. I. The leak was measured from a platinum 
wire PF to a tliin cylinder of platinum AB surrounding it. The cylinder was 
Fig. 1. PP, platinum wire; V, volt7ueter; CiC^Cs, commutators; R.-„ rheostat; Ct 3 , ammetei’; 
AB, cylinder ; K, key; RiR 2 R 3 R|, resistances ; CiG^, galvanometei’s ; S, shunt. 
I'4 centim. in diameter and 5 centims. long. The wire PP was in the form of a loop 
lianging vertically downwards. The cylinder was contained in a glass tul)e which 
* Ciui.D also made measurements in hydrogen and found the leaks greater in hydrogen than in air. 
He did not measure the temperature of his wire, so that his results are purely fpialitative. 
