VOL. LXVIII.] PHILOSOPHICAL TRANSACTIONS. 429 



fire, drawn off gradually from an electric cloud, was never known to do any 

 mischief, if the substance drawing it off had a good metallic communication 

 with the moist earth ; and that when any damage is done, it is occasioned by a 

 stroke of lightning, or in other words the electric fire of the charged cloud sud- 

 denly discharged through that body. 



Exp. 1. Mr. N. screwed a brass ball, of 4 inches diameter, at the end of the 

 rod D, then placed it nearly in contact with the ball c, at the end of the artificial 

 cloud; on charging the artificial cloud, the electric fire struck from the ball c 

 to the ball at the end of the rod, and continued striking all the while it was 

 gradually removing to the distance of \l-\ inches, and sometimes on to IQ or 



20 inches. 



Exp. 2. The apparatus remaining as in the last experiment, he changed the 

 ball of 4 inches diameter on the rod d, and in its stead screwed a ball of one inch 

 diameter; he then placed this very near to the ball c as before: on charging the 

 artificial cloud, the electric fire now struck to the ball at the end of the rod d 

 of 1 inch diameter, and continued striking while it was gradually removing to 

 the distance of about 2 inches. It then gave over striking, and was succeeded 

 by a hissing noise and a continued light on the 1 inch ball, while it was removing 

 very gradually from the ball c, till the distance between the two balls was about 

 10 inches; the hissing noise then ceased, and the light disappeared on the inch 

 ball. It now began to strike again, and continued striking to the inch ball all 

 the time it was very gradually removed, till the distance was about \4.-^ inches; 

 and sometimes would continue to strike to i6yV inches. 



Exp. 3. The apparatus remaining as in the last experiment, the ball of 1 inch 

 diameter was changed for one of -^ of an inch diameter. This small ball was 

 also placed nearly in contact with the ball c : on charging the artificial cloud, 

 the electric fire struck to this ball, and continued striking to it while it was very 

 gradually removed to the distance of half an inch ; beyond that, it would not 

 strike to it. But the ball was luminous all the while it was removed beyond the 

 striking distance as far as 33 inches. 



Exp. 4. The apparatus remaining as in the last experiment, but only changing 

 the ball of -^, for a wire about 31 inches long, terminating in a point: on 

 charging the artificial cloud, he could not now get the electric fire to strike the 

 point, though the point was almost in contact with the ball c; but when it was 

 about half a tenth of an inch distant from it, then the electric fire ran in a very 

 small stream to the point; but beyond that distance, though moved very gra- 

 dually, it was only luminous, and continued so at the point all the while it was 

 gradually removing to the distance of 6 feet from the ball c, at the end of the 

 artificial cloud. 



