308 Royal Society : — 



Feb. 13. — Eear-Admiral Eichards, C.B., "Vice-President, in the 



Chair. 



The following communication was read : — 



"On a new Eolation between Heat and Electricity." By Fre- 

 derick Gruthrie. 



It is found that the reaction between an electrified body and a 

 neighbouring neutral one, whereby the electricity in the neutral 

 body is inductively decomposed and attraction produced, undergoes 

 a modification when the neutral body is considerably heated. 



Under many circumstances it is found that the electrified 

 body is rapidly and completely discharged. The action of dis- 

 charge is shown to depend mainly upon the following conditions : — 

 (1) the temperature of the discharging body, and its distance from 

 the electrified one ; (2) the nature ( + or — ) of the latter's 

 electricity. 



With regard to (1), it is shown that the discharging power of a 

 hot body di mini shes as its distance increases, and increases with its 

 temperature ; but, concerning the temperature, it is proved that 

 the discharging power of a hot body does not depend upon the 

 quantity of heat radiated from it to the electrified, body, but chiefly 

 upon its quality. Thus a white-hot platinum wire connected with 

 the earth may exercise an indefinitely greater discharging power, 

 at the same distance, than a large mass of iron at 100° C, though 

 the latter may impart more heat to the electrified body. 



Neither the mere reception of heat, however intense, by the 

 electrified bod} r , unless the latter have such small capacity as to 

 be itself intensely heated, discharges the electricity if the source 

 of heat be distant ; nor is discharge effected when the electrified 

 body and a neighbouring cold one are surrounded by air through 

 which intense heat is passing. But, for the discharge, it is 

 necessary that heat of intensity pass to the electrified body from 

 a neutral body, within inductive range. 



White- and red-hot metallic neutral bodies exercise this dis- 

 charging power even when isolated from the earth, but always 

 with less facility than when earth-connected. 



The hotter the discharging body, whether isolated or earth- 

 connected, the more nearly alike do + or — electricities behave in 

 being discharged ; but at certain temperatures distinct differences 

 are noticed. The — electricity, in all cases of difference, is 

 discharged with greater facility than the -f- . 



Attempts are made to measure the critical temperatures at 

 which earth-connected hot iron (1) discharges + and — electricity 

 with nearly the same facility, (2) begins, as it cools, to show a 

 preferential power of discharging — , and (3) ceases to discharge 

 — • The temperatures so obtained are measured by the number 

 of heat-units, measured from 0° C, in 1 gram of iron of the 

 respective temperature, represented by the value of the expression 

 Fe 2,'oU. 



It is shown that various flames, both earth-connected and 



