High Potential Batteries for small currents. 327 



primary terms) involve the product w V, whereas the new 

 terms containing e involve V 2 and uq 2 . Hence if V is very large 

 or very small compared with u , the terms containing e may 

 be larger than the primary terms, even when e is as small as it 

 is for the planets. It is thus theoretically desirable to carry 

 the expansion as far as this point. But there is not much 

 object in going further, since the terms in e 2 , e 3 , etc. involve 

 no new combinations of the velocities V and u , and are 

 therefore necessarily of lower order of magnitude. 



The part of the motion of perihelion div=u 2 6/2c 2 is of 

 particular interest, since it is independent of the sun's 

 motion through the aether. It has therefore appeared in 

 some relativity theories of planetary motion, given by 

 de Sitter, Silberstein, and others. For Mercury it gives 

 just one-sixth of the observed discordance of perihelion ; 

 for Venus and the Earth it is negligible compared with 

 observational errors, on account of their small eccentricities. 



The other terms involving the eccentricity cannot be of 

 great importance unless V is very much greater than u . In 

 that case the primary and secondary terms are both extremely 

 large ; and, though they might happen to cancel for one 

 planet, it is scarcely possible that they should so nearly 

 neutralize one another for all the eight elements of the four 

 inferior planets. So far as I can see, the conclusions of my 

 previous paper are not materially modified by this more 

 rigorous calculation. 



XXXIII. High Potential Batteries for supplying small 

 currents. By Frank Horton, ScH., Professor of Physics 

 in the University of London*. 



r |TEE difficulties attending the use of a high-potential 

 -L battery capable of supplying a current of a few milli- 

 amperes are familiar to all who have experimented with the 

 discharge of electricity through gases. The type of battery 

 most commonly employed for this purpose is one consisting 

 of a number of small secondary cells with lead plates, and 

 the trouble usually experienced is the " rotting " of the lead 

 of the positive plate at the point where it passes through the 

 cover of the cell. The rotting consists in the formation of a 

 white powder which analysis shows to consist mainly of lead 

 sulphate, and this goes on until in a few months, or even 

 weeks, the rod is separated into two pieces. The rapidity 

 of this action depends ou the quality of the lead used in the 



* Communicated by the Author. 



