VOL. LXVIII.] PHILOSOPHICAL TRANSACTIONS. 4/5 



give a very strong shock : this proves, that the electric matter did not absolutely 

 pass through the glass, but only acted on the electricity inherent in it, in the 

 manner explained by Dr. Franklin. 



The direction of the electric matter, in the discharge of the Leyden bottle, 

 has been shown in a variety of methods (see Philos. Trans, vol. 64 and 67 ;) 

 but I shall here mention one which is a very curious addition to the number. 

 Mr. Lullin, of Geneva, placed 2 wires, the one upon, the other under, a card, 

 being about an inch from each other. This apparatus being made a part of the 

 circuit, a charged bottle of a proper size was discharged through it : when the 

 charge passed along the surface of the card, from the end of that wire into 

 which it was discharged, till it came to the end of the other wire, and there 

 j)ierced a hole through the card, passing by that wire to the negative side of the 

 bottle ; and this happened whether the bottle was charged positively or nega- 

 tively. A learned and ingenious correspondent of mine, the hon. Frederic 

 Christian Mahling, counsellor of state at Copenhagen, has improved this ex- 

 periment, by first painting the card in a line about half an inch broad on each 

 surface with vermillion. The charge passing in this line (the card being 

 previously well dried) shows its passage by a black mark on the vermillion, the 

 mark being on one side of the card when the bottle is charged positively, and 

 on the other side of it when the bottle is charged negatively. To which I would 

 add, that a line of light is seen on one surface of the card through the whole 

 space between the ends of the wires in one case, for instance, when the bottle 

 is charged positively. But no light is seen in the other case, that is, when the 

 bottle is charged negatively, till the electricity bursts a hole through the card to 

 get at the wire which is in contact with the negative side of the bottle, as in this 

 case the charge passes along the under surface of the card. If the card be placed 

 vertically between 2 insulated wires, as in the universal discharger, described in 

 Mr. Cavallo's Treatise on Electricity, the experiment may be made with great 

 facility and certainty. The card may be fixed on a bit of sealing wax, or set in 

 a piece of wood, sawn to a proper depth with a fine tenon saw. 



L. Track of His Majesty s armed Brig Lion, from England to Davis's Streights 

 and Labrador, ivith Observations for determining the Longitude by Sun and 

 Moon and Error of Common Reckoning ; also the I ariation of the Compass 

 and Dip of the Needle, as observed during the said Voyage in 1776. By 

 Lieut. Richard Pickersgill, late Commander of the said Vessel, p. 1057. 

 This is a copy of the commander's journal of the voyage, comprising, in dif- 

 ferent columns, the day and hour, the latitude, the longitude by the observation 

 and the ship's reckoning, the temperature by the thermometer, the observed alti- 



3 p 2 



