298 



Mr. J. Buchanan on Hot Gases 



gas issued from a very narrow horizontal slit, giving a flame 

 as nearly " linear " as possible. To protect the flame from 

 draughts of air, and also to ensure that no electrical dis- 

 turbance could arise from outside influences, the flame and 

 platinum pieces were surrounded by a metal cylinder, open 

 at both ends, of about 10 centirn. diameter and 36 centim. 

 high, which was permanently connected to earth by a wire. 

 The position of the cylinder is indicated by the dotted circle 

 round c in the figure. The stem of the gas-burner, and the 

 wires from the pieces of foil passed through holes in the side 

 of the cylinder without touching it. 



In the first regular experiments that were made the 

 respective pairs of quadrants of the electrometer were joined 

 to the binding-screws of the condenser, one pair of quadrants 

 being as usual connected to earth. The condenser was then 

 charged ; 4 Leclanches sending the spot of light near to the 

 end of the scale. The flame being in action, the battery was 

 disconnected and the scale-readings taken at equal intervals 

 of time until the spot of light was down to near the zero. 

 From these readings the rate of " leakage " could be found. 

 Obviously the range of potentials was very limited. 



For the later experiments, specimens of whose results are 

 given below, an arrangement was suggested to me by Prof. 

 G. C. Foster, F.R.S., which is applicable to much wider 

 ranges of potential. 



earth 



The figure gives a diagram of the connexions. The 

 binding-sere iv B of the condenser was kept in connexion 

 with one electrode, Q, of the battery ; the other electrode, P, 

 with the earth and with one pair of quadrants ; whilst the 

 other binding-screw, A, of the condenser was connected to 

 the insulated pair of quadrants during the whole of each set 

 of observations. 



Before beginning a set of readings, the two pairs of 

 quadrants of the electrometer were put into connexion with 



