Induction of instantaneous Electric Currents. 507 



the cause of those different effects, although remote, depended 

 on the different capacity of the jars ; for the large jars, with dis- 

 continuous external coatings, may be considered as furnished 

 with small electric capacities only, as many of these small squares 

 remain idle in charging or discharging the jars themselves. 



Considering, then, that the least capacity of the confining 

 coatings involves as a consequence, that with similar charges, 

 that is, furnished with an equal quantity of electricity, the 

 spark must pass to a greater distance, and thence find a similar 

 expenditure in the longer space of air which it must traverse, 

 I wished to see, if by effecting a retardation in the discharges 

 of the large jars, there might perhaps be the same direction of 

 the induced current that was observed with jars of less power. 



I therefore caused the discharges of the large jars to pass 

 through the water in a glass before reaching the actuating 

 wire; and I saw that in this case these jars acted as those 

 furnished with much less capacity. It is singular to see how 

 the same quantity of electricity, put in motion by the same 

 jar, induces a current, either in one direction or in that pre- 

 cisely opposite, according as it is, or is not, made to pass 

 through a liquid stratum. 



The different velocity, then, with which the electricity dis- 

 charges itself from the one coating to the other, seems to give 

 rise to the said inversions of phenomena : and in this opinion 

 I was confirmed by having many times observed, when expe- 

 rimenting with the bands of lead described in § XII., that a 

 jar of great power (capacitd) strongly charged and discharged 

 upon the actuating band, caused the induction contrary to 

 that of the little jars ; and with the first residual charge there 

 was no effect, with the second and third an opposite one. 



XX. A glass tube of about two centimeters in diameter, 

 and twenty in length, was filled with spring water, and closed 

 with two corks, through the axis of each of which passed a 

 brass wire so far as to touch the water ; both these wires pro- 

 jected out for the space of some centimeters, and terminated 

 in a little globe. Having duly dried the exterior of the tube, 

 and surrounded it with a band of lead two centimeters wide, 

 which was twisted round it three times in the middle part of 

 the tube* the ends of the bands were put in metallic commu- 

 nication with the extremities of the re-electrometric wire. 

 Having discharged the Leydeh jar so that it must pass through 

 the water of the tube, I brought the external coating into 

 contact with the little globe of one of the said wires, and the 

 internal* with the little globe of the other, and the needle 

 deviated two degrees. 



[* Jrmaltira externa in the original, but obviously in error. — Edit.] 



