448 Dr. G. Gore on the Influence of Proximity 



temperature varying in different cases from 5 to 16 Centi- 

 grade degrees above that of the apparatus, and placed in 

 immediate contact with the glass tubes above the u A " and 

 " B " electrodes separately, and allowed to remain a sufficient 

 period of time. In each of the five trials, including a total 

 of 28 observations, the heat made the electrodes negative ; 

 i. e. it decreased the electromotive force at the positive " A 

 electrodes, and increased that at the negative " B " ones, and 

 thus in every case it produced an opposite effect to that pro- 

 duced by the lead. In one of the experiments, with the 

 warmed strip of lead at a temperature of lb' Centigrade 

 degrees above that of the apparatus, the difference of deflexion 

 produced was equal to 32 degrees on the galvanometer scale ; 

 and in two instances the effect of the heat upon the current 

 reached its maximum in about 1 5 to 20 minutes. The tempera- 

 ture of the room w^ould not account for much of the effect, 

 because it affected both sets of electrodes equally ; a rise of 

 it increased the current, not by increasing the voltaic action, 

 for the reason just mentioned, but by diminishing the con- 

 duction-resistance of the liquid, and in averaging the results 

 an allowance of five degrees of average deflexion on the gal- 

 vanometer scale had to be made for each Centigrade degree 

 average rise of temperature. These results prove that the 

 permanent effect of the proximity of the lead upon the voltaic 

 action was not due to heat from any source. At one period 

 readings were constantly and regularly taken of a very sensitive 

 thermometer placed upon the glass bulbs of the apparatus 

 and plotted as curves, and these curves w r ere compared with 

 curves representing the changes of the voltaic current, and 

 with curves of that current whilst under the influence of the 

 lead bars. On all subsequent occasions also observations of 

 the temperature of the apparatus were taken simultaneously 

 w T ith those of the amounts of galvanometric deflexion. 



As in each of four different experiments the light and heat 

 of burning magnesium, at a distance varying from three to 

 six inches from the nearest electrodes, slightly decreased 

 their electro-positive state, the light and heat had an opposite 

 effect to that of the influencing bars. 



[Whether temperature affects gravitation is an interesting- 

 question. " Von Sternack found, on comparing his observa- 

 tions in two mines, that the increase of gravity on descending 

 was much more nearly in proportion to the rise of tempera- 

 ture than to the depth of descent." (H. Poynting, ' A History 

 of the Methods of Weighing the Earth,' Proc. Birmingham 

 Phil. Soc. vol. ix. p. 13.)] 



