for multiplying and maintaining Electric Charges. 393 



repulsion of the receiver and upward attraction of the inductor. 

 The potential method gives the integral amount, being the excess 

 of work done against electric force, above work performed hy elec- 

 tric force on each drop in its whole path. It is of course equal 

 to mY, if m denote the quantity of electricity carried by each 

 drop, as it breaks from the continuous water above, and V the 

 potential of the inner coating of the lower jar, the potential of the 

 uninsulated water being taken as zero. The practical limit to 

 the charges acquired is either when one or other of them is so 

 strong as to cause sparks to pass across some of the separating air- 

 spaces, or to throw the drops of water out of their proper course 

 and cause them to fall outside the receiver through which they 

 ought to pass. It is curious, after commencing with no electricity 

 except a feeble charge in one of the jars, only discoverable by a 

 delicate electrometer, to see in the course of a few minutes a 

 somewhat rapid succession of sparks pass in some part of the ap- 

 paratus, or to see the drops of water scattered about over the lips 

 of one or both the receivers t 



Ym. 2. 



The Leyden jars represented in the sketch (fig. 2) are open- 

 mouthed jars of ordinary flint glass, which, when very dry, I gene- 

 rally find to insulate electricity with wonderful perfection. The 

 inside coatings consist of strong liquid sulphuric acid, and heavy 

 lead tripods with vertical stems projecting upwards above the 

 level of the acid, which, by arms projecting horizontally above the 

 lip of the jar, bear the inductors and receivers, as shown in fig. 2. 

 Lids of gutta percha or sheet metal close the mouth of each jar, 

 except a small air-space of from J to J of an inch round the pro- 



Phil. Mag. S. 4. Vol. 34. No. 231. Nov. 1867. 2 D 



