430 PHILOSOPHICAL TRANSACTIONS. [anNO 1778. 



Exp. 5. The apparatus still remaining, only changing the wire, for the ball 

 of 4 inches diameter, used in the first experiment, having now a small hole 

 through it. Mr. N. then put into this hole a wire, leaving the end^ which 

 terminated in a fine point, projecting out only a 10th of an inch beyond the 

 surface of the ball, and directly pointing to the ball c: on charging the artificial 

 cloud, the ball with the point being first placed nearly in contact with the ball c, 

 it was then gradually removed; but not at any distance would it strike to the 

 ball, or the point projecting out of it. The point was luminous at the distance 

 of 30 inches. 



Exp. 6. Every thing remained the same as in the last experiment, except only 

 that he now pressed in the point, till it was even with the surface of the 4 inch 

 bal : on charging the artificial cloud, the electric fire now struck to the ball at 

 any distance, from being nearly in contact, all the while it was very gradually 

 removed to as far as 17^ inches, though before in the last experiment, where 

 the point projected from the ball only the 10th of an inch, it would not strike 

 at any distance. 



Exp. 7 • The apparatus remaining as in the last experiment, Mr. N. took a 

 ball of 3-1- inches in diameter, which had a small hole through it, and screwed 

 it to a hollow brass stem. He then put into this hole one end of a wire, and 

 the other end, which was pointed, projected one inch beyond the surface of the 

 3-L inch ball. This ball and stem, with the pointed wire to it, lie fixed to a stand 

 covered with tin-foil; having a good metallic communication with the earth, he 

 placed this stand so that the point was directly opposite to the side of the artifi- 

 cial cloud, and exactly at 5 feet distance from it: then, on charging the artificial 

 cloud, the greatest striking distance from the ball c to the ball of 4 inches 

 diameter, on the receiving rod d, was found to be 1 Q-^ inches. 



Exp. 8. Every thing continued as in the last experiment, only now he drew 

 the wire out of the ball and stem so far that the point projected Q inches beyond 

 it; on charging the artificial cloud, the greatest striking distance now was found 

 to be S-iV inches. 



' Now, in order to see how far a point, or different sized balls fixed on the 

 stand, and having a very small separation in the metallic conmiunication with 

 the earth, would visibly act to carry off the electric fire of the artificial cloud, 

 Mr. N. made the following experiment. 



Exp. Q. He took a stick of common sealing-wax, and having fixed a screw to 

 each end, he ])asted a slip of tin-foil the whole length of the surface, and having 

 made a separation of the foil of about a 50th of an inch, he screwed the pointed 

 wire into one end, and the other end of the wax to the brass rod, where the 

 bull with the point projecting from it was placed in the last experiment. He 



