VOL. LXXVIII.] PHILOSOPHICAL TRANSACTIONS. 357 



cise and certain. After repeating Mr. Bennet's description of his doubler, Mr. C. 

 adds, as soon as I understood the principle of this contrivance, I hastened to con- 

 struct such an apparatus, to try several experiments of a very delicate nature, 

 especially on animal bodies and vegetables, which could not have been attempted 

 before, for want of a method of ascertaining exceedingly small quantities of elec- 

 tricity ; but, after a great deal of trouble, and many experiments, I was at last 

 forced to conclude, that the doubler of electricity is not an instrument to be de- 

 pended on, for this principal reason ; viz. because it multiplies not only the elec- 

 tricity which is willingly communicated to it from the substance in question ; but 

 it multiplies also that electricity which in the course of the operation is almost 

 unavoidably produced by accidental friction ; or that quantity of electricity, how- 

 ever small it may be, which adheres to the plates in spite of every care and pre- 

 caution. 



Having found, that with a doubler constructed in the above manner, after 

 doubling or multiplying 20 or 30 times, it always became strongly electrified, 

 though no electricity had been communicated to it before the operation, and 

 though every endeavour of depriving it of any adhering electricity had been 

 practised ; I naturally attributed that electricity which appeared after repeatedly 

 doubling, to some friction given to the varnish of the plates in the course of the 

 operation. In order to avoid entirely this source of mistake, or at least of sus- 

 picion, I constructed 3 plates without the least varnish, and which of course 

 could not touch each other, but were to stand only within about 4- of an inch of 

 each other. To effect this, each plate stood vertical, and was supported by 2 

 glass sticks, which were covered with sealing-wax. I need not describe the man- 

 ner of doubling or of multiplying with those plates ; the operation being essen- 

 tially the s^me as when the plates are constructed according to Mr. Bennet's 

 original plan, excepting that, instead of placing them one on the other, mine 

 are placed facing each other. Sometimes, instead of touching the plates them- 

 selves with the finger, I have fixed a piece of thin wire to the back of the plate, 

 and have then applied the finger to the extremity of the wire, suspecting that 

 some friction and some electricity might possibly be produced when the finger 

 was applied in full contact to the plate itself. 



Having constructed those plates, Mr. C. thought he might proceed to perform 

 the intended experiments without any further obstruction ; but in this he found 

 himself quite mistaken : for, on trying to nmltiply with those new plates, and 

 when no electricity had been previously communicated to any of them, he found, 

 that after doubling 10, 15, or at most 20 times, they became so full of electricity 

 as to afford even sparks. All his endeavours to deprive them of electricity proved 

 ineffectual. Neither exposing them, and especially the glass sticks, to the flame 

 of burning paper, nor breathing on them repeatedly, nor leaving them untouched 



