354 VHILOSOPHICAL TRANSACTIONS. [aNNO 1739. 



To be certain that the rubbed tube is made electrical, I pass my fingers near 

 it after rubbing, to hear- whether it snaps ; but always rub again before I apply 

 it ; because by snapping it loses its electricity at the place where it snaps. 



Exper. 3. — When I rubbed the tube ab, it would then attract the thread 

 of trial T between a and b ; but not at all above a or below b, unless when I 

 applied the tube gg above a : then the thread of trial would be attracted by 

 the plate dd, and the top of the great tube from a to a, but no lower. It 

 would also be attracted by all the bar hh, and only 3 or 4 inches below h. 



Exper. 4. — Having filled the tub ab with water, the electricity of the rubbed 

 tube GG, applied at a, ran strongly down the tube ab, and impregnated the ball 

 c, so as to make it strongly attract the thread of trial, while the balls c, c, re- 

 ceived no virtue at all. But on wetting the cat-gut strings h, c, with a sponge, 

 all the 3 balls c, c, c, strongly received the electrical virtue. 



Exper, 5. — I took away the bar hh, and its balls and strings ; and having 

 well dried the tube, I rubbed it, and hung it up as before ; so that it would 

 snap, or attract the thread from a to b, but no where else. 



Then putting the small bar hh into the middle of the tube ab, in its axis, 

 represented by the pricked line, on application of the rubbed tube gg at a, the 

 virtue was immediately communicated to the ball c. The same thing happened 

 when instead of the bar, a brass wire, a walking cane, a small green stick, or 

 small packthread, was placed in the axis of the tube. 



Exper. 6. — 1 took a barometer tube, empty, and very dry, and placed it in 

 the axis of the great tube ab ; but it would conduct no electricity to the ball c; 

 though it carried it down very readily when full of water, though quite dry on 

 the outside. 



Another small tube, open at both ends, which conducted no virtue to c 

 when dry, being only moistened a little by the breath in blowing through 

 it, carried down the virtue from a to c very strongly. 



All this while the cat-gut strings e, e, received no electrical virtue. 



Definition 1 . — A body electrical per se, is such a body in which one may 

 excite electricity by rubbing, patting, hammering, melting, warming, or any 

 other action on the body itself, as amber, sealing-wax, glass, resin, sulphur, &c. 

 besides many, if not all, animal substances. 



Defin. 1. — A non-electrical, is such a body as cannot be made electrical by 

 any action on the body itself immediately ; though it is capable of receiving 

 that virtue from an electrical per se. 



Observations. — 1 . When the air is full of moist vapours, electrics per se are 

 excited to electricity with very great difficulty, requiring to be often warmed, 

 and much rubbed ; as appears in exciting that virtue in glass, amber, wax, &c. 



