358 PHILOSOPHICAL TRANSACTIONS. [aNNO 1788. 



for several days, and even for a whole month, during which time the plates re- 

 mained connected with the ground by means of good conductors, nor any other 

 precaution he could think of, was found capable of depriving them of every vestige 

 of electricity ; so that they might show none after doubling 10, 15, or at most 20 

 times. The electricity produced by them was not always of the same sort ; for 

 sometimes it was negative for 2 or 3 days together ; at other times it was positive 

 for 2 or 3 days more ; and often it changed in every operation. This made him 

 suspect, that possibly the beginning of that electricity was derived from his body, 

 and being communicated by the finger to the plate that was first touched, was 

 afterwards multiplied. In order to clear this suspicion, he actually tried those 

 plates at different times, viz. before and after having walked a great deal, before 

 and after dinner, &c. noting very accurately the quality of the electricity produced 

 each time : but the effects seemed to be quite unconnected with the above-men- 

 tioned concomitant circumstances; which independence was further confirmed by 

 observing that the electricity produced by the plates was of a fluctuating nature, 

 even when, instead of touching the plates with the finger, they had been touched 

 with a wire, which was connected with the ground, and which he managed by 

 means of an insulating handle. 



At last, after a great variety of experiments, Mr. C. became fully convinced 

 that those plates did always retain a small quantity of electricity, perhaps of that 

 sort with which they had been last electrified, and of which it was almost im- 

 possible to deprive them. The various quality of the electricity produced was 

 owing to this, viz. that as one of those plates was possessed of a small quantity of 

 positive electricity, and another was possessed of the negative electricity, that plate 

 which happened to be the most powerful, occasioned a contrary electricity in the 

 other plate, and finally produced an accumulation of that particular sort of elec- 

 tricity. These observations evidently show, that no precise result can be obtained 

 from the use of those plates, and of course that when constructed according to 

 the original plan, they are still more equivocal, because they admit of more 

 sources of mistake. 



As those plates, after doubling or multiplying only 4 or 5 times, show no signs 

 of electricity, none having been communicated to them before, he imagined that 

 they might be useful so far only, viz. that when a small quantity of electricity is 

 communicated to any of them in the course of some experiment, one might mul- 

 tiply it with safety 4 or 5 times, which would even be of advantage in various 

 cases, but in this also his expectations were disappointed. Having tried them in 

 various experiments, Mr. C. then adds, after all the above-mentioned experiments 

 made with those doubling or multiplying plates, we may come to the following 

 conclusion, viz. that the invention is very ingenious, but their use is by no means 

 to be depended on. It is to be wished, that they may be improved, so as to ob- 



