1885.] arrangement for maintaining a constant high potential. 229 



plates, and this, I take it, is most easily accomplished by a spring 

 hung from a Weber suspension in a tube which will protect it from 

 atmospheric disturbances. 



When everything is properly adjusted the plate ought to settle 

 down into a state of pretty rapid vibration, so that the mean 

 potential difference say during each minute is constant. I had at 

 one time intended to make the movable disc insert or remove a 

 varying resistance ; as for instance by making the contact points 

 conical. There were however many mechanical difficulties : and 

 worse than that the constancy of the battery would have required 

 attention in any continuous regulator. Moreover unless a spring 

 of peculiar construction was used the upper plate would be un- 

 stable, and this would be fatal. The only way of guarding against 

 it would be by arranging the ratios of the resistances taken in aud 

 out; bat this would have been impossible even supposing the 

 current was not strong enough to heat the wires so as to pro- 

 duce a continuous change. For all practical purposes however a 

 constant integral value of the potential is all that is required, 

 and this may be obtained from a discontinuous governor. The 

 drawings are not to scale, because the scale as already pointed out 

 will depend on the purpose for which the governor is to be used. 



March 16, 1885. 



Prof. Foster, Pkesident, in the Chair. 



The following were elected Fellows : 

 Prof. J. J. Thomson, M.A. 

 J. M. Dodds, ALA. 

 Rev. A. H. Cooke, M.A. 

 A. E. Shipley, B.A. 



The following communications were made to the Society : 

 (1) Further remarks on the Urea-ferment. By A. S. Lea, M.A. 

 In the previous communication made to the Society it was 

 stated that although the Torula ureae contains a ferment which 

 is soluble in water, this ferment is not to be found in the fluid 

 surrounding the cells either during or after an active alkaline 

 fermentation. It appears therefore that the cells do not carry on 

 the fermentation by excreting the ferment with the surrounding 

 fluid, but that its activity is localised in the substance of the cells. 

 The absence of the ferment in the fluid during an active ferment- 

 ation appeared at first sight somewhat unexpected, in view of 



