VOL. LXIV.] PHILOSOPHICAL TRANSACTIONS. 501 



these experiments, Mr. N. mentions a caution, which may be of service to 

 future electricians who may use large batteries. It is, never to discharge their 

 batteries, if it is through a ready conductor, unless the charge passes at least 5 

 feet from the inside of the battery to the outside; by making use of this 

 precaution, which he learnt from experience, he has discharged the battery near 

 100 times, and never broke a single jar, by the electrical discharge; before 

 which he was continually breaking them, by discharging the battery in the 

 common method. 



There is another experiment, which he mentions, as it probably may give 

 some light in respect to balls, or points, for conductors, for buildings or ships : 

 the apparatus and manner of trying the experiments, is as follows: in fig. l, 

 pi. 10, A represents the end of the large conductor of the electrical machine; 

 B a brass ball screwed into the end of it, of 1 -pV inch diameter ; c a small 

 conductor, which was 5 feet 11 inches long, and 1-^ inch diameter; it was 

 made of wood, covered with tin foil, and was insulated, by being supported on 

 a stand, the part d of which was of solid glass. The ball e, at the end of this 

 conductor, was 3 inches diameter, and the ball p l-jV inch diameter; under this 

 ball F, was a stand g, made of wood covered with tin foil, having a moveable 

 part H, which might be raised higher or lower. On the top of this moveable 

 part was screwed, either a pointed wire, or a wire with a ball ^ of an inch 

 diameter, and from the bottom of this stand a chain passed along the floor, till 

 it was connected with the chain, which hung from the cushion : he then placed 

 the conductor c, so that the ball e was 4 inches distance from the ball b ; and 

 having screwed into the top of the moveable part h, of the stand g, a pointed 

 wire, he moved it till the point was directly under the ball f, at the distance of 

 3 or 4 inches; and, on exciting the electrical machine, the fire passed from the 

 ball B, to the ball e, and almost at the same instant struck on the point from ■ 

 the ball f. He increased the distance slowly between the point and the ball f, 

 till he found the utmost distance to which it would strike to the point, which 

 was 6 inches; he continued to move the point to Q inches distance or more; it 

 then was luminous, and the fire continued to strike from the ball b, to the ball 

 E ; which showed that the point carried off all the electrical fire from the con- 

 ductor c, otherwise it would not continue to strike from b to e. He then 

 removed the point, every thing else remaining as before, and in its stead 

 placed a wire, with a ball of ^ of an inch diameter, at the top of it, at the 

 distance of 3 or 4 inches, directly under the ball f, in the same manner as the 

 point; then, on increasing this distance slowly, the electrical fire was found to 

 strike to the ball at 9 inches, which is half as far again as to the point, and with 

 this remarkable difference, that the quantity of fire was much greater, and 



