VOL. LXVIII.] PHILOSOPHICAL TRANSACTIONS. 4(33 



much the readier if you strew a few line particles of brass on it. The pin 

 dust is the best for this purpose; but as this oil is scattered about by the explosion, 

 and, when kindled, fills the room with much more smoke than the powder of 

 resin, I prefer the last. 



This experiment may be made use of for lighting a candle in the night as well 

 as in the day. But for this purpose a charged phial should always be kept in 

 readiness, and placed where it may be easily found in the dark. The jar for this 

 purpose should be furnished in the manner invented by Mr. Cavallo, with a glass 

 tube at the inside, reaching from the mouth of the phial to the bottom, through 

 which tube the wire which establishes the communication with the inner coat- 

 ing passes, which, as soon as the phial is charged, is to be taken away, by 

 holding it by the piece of sealing-wax, or glass rod covered with sealing-wax, 

 fastened to the knob of the wire, which wire is only to be put into the glass 

 tube again when the phial is to be discharged. Mr. Cavallo finds, that this jar 

 will keep its charge a month, if the glass tube, and likewise the jar where it is 

 not coated, are carefully lined with sealing-wax both within and without. A jar, 

 containing 6 or 8 pints, fitted up in this manner, may be kept as a magazine of 

 electrical fire, and a little coated phial, just large enough to light a candle, may 

 be occasionally applied to it on purpose to light the powder of resin. As soon as 

 this little phial is charged, which is done in an instant, the wire must be taken 

 out of the large jar or magazine, to keep the remainder of the charge, which 

 may serve afterwards for several charges of the little phial. 



I have often carried in my pocket such a little jar a whole day, on purpose to 

 fire a kind of pistol loaded with inflammable air in the manner described by 

 Mr. Volta, of Como. A phial of about 2 ounces contained electrical fire 

 enough to kindle such a pistol 20 times. In order to take out only as much of 

 the electrical charge as was wanted for this purpose, I plunged into the glass tube 

 of the charged phial a small glass tube, 4 inches long, adapted as a Leyden 

 phial, by sticking in it at the bottom, which is hermetically sealed, a bit of tin- 

 foil, an inch long, coiled up, and pasting a similar bit at the outside: a thin wire 

 passed through the tube from the inside tin-foil to the opening, which was shut 

 by a smooth brass ball stuck to it, and in contact with the said wire. The 

 outside part of this tube, which was not coated with tin-foil, was lined or 

 varnished with sealing-wax. ^ 



XLVIII. Electrical Experiments, to explain how ftxr the Phenomena of the 

 Electrophorus may be accounted for by Dr. Franklins Theory of Positive and 

 Negative Electricity ; being the Annual Lecture instituted by the (Fill of 

 Henry Baker, Esq., F. R.S. By John Ingenhousz, M. D., F. R. S. p. 1027. 

 Having had the honour of being appointed, by the President and Council of 



