163 PLYMOUTH INSTITUTION. 



October 24th. — Mr. W. S. Harris, in this paper, treated of the 

 probable nature of electrical action, &c., and considered that the 

 hypothesis of a single indivisible agency is favorable to an easy ex- 

 planation of the observed phenomena. Some new electrical instru- 

 ments were exhibited to the society ; an electroscope, an electrometer, 

 and an adaptation of the simple balance to the weighing of electrical 

 attraction. Considering that electrical agencies would be greatly 

 facilitated by an accurate method of measuring comparative quanti- 

 ties of electricity, the lecturer has endeavoured to arrive at what may 

 be considered a unit of measure, and proposes, for this purpose, a 

 small Leyden jar, inverted on the conductor of the machine, from 

 the outer coating of which the electricity is communicated to a 

 larger jar or battery. This unit jar being furnished with discharg- 

 ing balls, the experimentalist is enabled to measure, by the number 

 of small explosions, the quantity accumulated. 



Comparative quantities are disposed upon simple conductors by 

 means of an insulated jar, charged with a known quantity; from 

 the positive or negative coating of which, sparks are drawn upon an 

 insulated transfer plate. 



Some curious results have been arrived at in electricity by this 

 method of research. Thus it was found that, in disposing quanti- 

 ties of electricity on simple or compound conductors, the attractive 

 force evinced was as the square of the quantity directly, and the 

 quantity being constant as the square of the surface inversely. 

 These laws are general for perfectly similar conductors, but they do 

 not apply to every case. Extension in length contributes to increase 

 the capacity of a conductor : the lecturer has examined this curious 

 fact, and has found that the intensity varies with the area and 

 boundary of a plane surface inversely ; and that the capacity of a 

 cylinder for electricity is the same as that of a plane surface of equal 

 area ; he also finds that the capacity of a sphere is the same as that 

 of a circle of equal area : and that to have conductors of double, 

 treble, &c., capacities, the plane conductors, into which they may 

 be supposed to be rectified, must be such that the linear extension 

 and superficial dimensions must also be double, treble, &c., of cacli 

 other. 



The lecturer concluded this paper by some observations on the 

 general law of electrical attraction, and of the attraction of spheres 

 and other bodies, accompanied by most beautiful and successful 

 experi^iental illustrations, some account of which we hope to lay 

 before our readers in a future number. 



