312 PHILOSOPHICAL TRANSACTIONS. [aNNO iJSQ. 



the lower parts, may be able to draw them upwards, till the excess of weight, 

 which is constantly increasing, is equal to the excess of attraction. 

 Prop. III. Bodies, made Electrical by rubbing, do themselves repel one another, 

 or the electrical excited Bodies themselves repel one another. 



Exper. 1 . The two fragments of tubes before mentioned, prop. 2, exper. 8, 

 being suspended horizontally, and in a position parallel to each other, Mr. W. 

 held in one hand, and with the other rubbed some time ; then gently letting 

 them go so as to be at rest, they receded from each other towards that end 

 which had not been taken hold of. 



Also, he suspended a single little tube, about a foot long, by a long blue silk 

 line, perpendicularly, and on a table placed the great tube fixed in a stand as 

 before, and excited each alternately, 2 or 3 times ; then gently moved the tube 

 with the stand it was fixed in, near the suspended little one : the little tube ma- 

 nifestly receded so much, that a cross blue silk line, stretched horizontally at 

 about an inch distance on the opposite side, would sometimes, on the tirst ap- 

 proach of the great tube, be touched by it. 



Exper. 2. Three scarlet silks, each pendulous by loops from a cross silk 

 line, and close together, being rubbed downwards two or three times, between 

 the finger and thumb, showed a considerable repulsive force with regard to each 

 other, forming themselves immediately into a triangular pyramid, and conti- 

 nuing in this state of separation some time ; and, which shows their attraction 

 at the same time, with regard to other bodies not excited, coming to them 

 when brought near them. 



He observed the same repulsive force in 3 yellow and 3 green silks, under the 

 same circumstances, and excited in the same manner, but not in so great a de- 

 gree as in scarlet. In blue the repulsive force was scarcely discernible after seve- 

 ral times rubbing. 



Scholium. Dr. Hales, in the 12th article of his 13th experiment, in the 2d 

 volume of his Statical Essays, observes, " That if a piece of one of the bronchiae 

 or gills of the muscle shell -fish, be cut off, and put into a small concave glass, 

 with three or four drops of its liquor, and be then placed under a double mi- 

 croscope, the blood may be seen greatly agitated in the fine vessels ; and at the 

 cut edge of the piece of gill, may with great pleasure be seen many blood-glo- 

 bules, repelled from the cut orifices of the blood vessels, and attracted by other 

 adjoining vessels : also other globules rolling round their centre, and repelling 

 each other ; whence (as he says) it is plain, that bodies, by brisk rubbing and 

 twirling about, may acquire, in a watry fluid, both attractive and repulsive virtue 

 or electricity." 



