VOL. LXVIII.] PHILOSOPHICAL TRANSACTIONS. 341 



directly under the nearer end of the great cylinder, so that the distance between 

 the point of the conductor and cylinder was little more than 4 inches, the ma- 

 chine was then put into motion. After about 1 turns of the wheel, a small 

 stream of light appeared at a little interval, between the top of the longest thick 

 wire which represented the bent spout, and its little cistern next to the gutter, 

 where the metallic communication was purposely interrupted. This stream con- 

 tinued to be visible, though the model was moved along the frame from its fixed 

 station to more than the distance of 43 inches. 



Exp. 2. When a conductor of the same length with the former, but rounded 

 at the end, and no more than -^ of an inch in diameter, was put in the place of 

 the pointed one, every other circumstance continuing the same, the small stream 

 of light appeared again ; but on moving the model a little beyond the distance 

 of 1 6 inches, it totally disappeared. 



First Observation. — By the 1st experiment it was manifest, that the point 

 acted on the charge all the time the model was moving through a space equal to 

 43 inches ; and consequently was, all that time, diminishing the charge in the 

 great cylinder. On the other hand, the 2d experiment showed, that the 

 rounded end acted on the charge only while the model moved through a space 

 equal to l6 inches. And from the 2 experiments compared, it appears, that a 

 charged body is exhausted of more of the fluid by a pointed, than by a blunted 

 conductor. 



Exp. 3. If in the place of the rounded conductor a similar one was put, but 

 about -i- of the length, while the model stood directly under the great cylinder 

 as before, the charge contained in it produced no appearance of light whatever. 



Exp. 4. But when a pointed conductor of the same length with the last was 

 put in its place, the small stream of light appeared, and continued visible all the 

 time the model was moved through a space equal to 18-i- inches. 



2d Observation. — These last experiments, compared with the former 2, show 

 that a rounded conductor, little more than 1-i- feet above the highest part of a 

 building, receives a far less quantity of the matter of lightning from a cloud 

 fully charged, than a pointed conductor placed 10 feet above a building, circum- 

 stanced alike in every other respect. Nay, a pointed conductor of the same 

 length with the short one that was rounded, appears, from these experiments, to 

 collect a greater quantity of the fluid, than even the long conductor with a 

 rounded end. 



Exp. 5. On repeating the 1st experiment with 10 turns of the wheel only, 

 the charge remaining in the great cylinder was immediately received on the hand; 

 the sensation it occasioned was little more than perceptible. — ivxp. 6. But on 

 repeating the 2d experiment with 10 turns of the wheel also, the charge remain- 

 ing was taken ; but the sensation in this case was increased considerably, — 



