456 Dr. G. Gore on the Influence of Proximity 



To find the average value of voltaic current plus that of 

 the effect of the substance : — On the second day, the tubes 

 being 5 inches distant from the bars, and the circuit having 

 been left open all night, the latter was closed in the 

 morning, and after five minutes the spot of light was 

 brought to zero. The tubes were then immediately slid into 

 the space between the bars, and the observations of de- 

 flexion and temperature taken forty times during the day 

 in the above manner. 



In order to correct the average values of the currents of 

 the first and second days for difference of temperature, an 

 allowance of five degrees of the average deflexion for each 

 Centigrade degree difference of average temperature of the 

 two days was made to bring the average temperature ot 

 the one day to that of the other. The corrected average 

 value of the voltaic current alone was then subtracted from 

 that of the voltaic current plus the effect of the substance, 

 in order to obtain the value of the latter. This was done 

 three times for each week, and the average of the three 

 taken as being the final value of effect of the particular 

 substance. 



In consequence of the final average number for each sub- 

 stance varying considerably with the age and amount of use 

 of the solution, I was unable to obtain a reliable series of 

 relative values of effect of all the substances ; but, by com- 

 paring the values obtained of substances immediately after 

 each other, it was found that heavy ones usually gave 

 greater effects than light ones, approximately in the fol- 

 lowing order : — copper ; wrought iron ; cast iron ; lead ; 

 bismuth and antimony ; flint glass ; brass and magnesium ; 

 zinc and slate ; ebony, deal, and plaster. This general 

 relation of behaviour of heavy substances and light ones 

 is not unlike that of their degrees of opacity to Rontgen 

 rays. As the effect did not approximate very strictly to the 

 order of the specific gravities of the substances, I venture to 

 suggest that whilst the greater proportion of effect may be 

 due to rays of gravity, other rays may assist in producing it; 

 it is also probable that the rays proceeding from one substance 

 differ somewhat in kind from those proceeding from another 

 and produce a different amount of voltaic change. 



Effect of Mass of Substance. 



With the object of ascertaining whether the influence 

 varied directly as the mass of the substance, or proceeded 

 only from its external surface, the effect of two sheets of 

 copper, 22 inches long, 2 inches wide, and *013 inch thick, 



