VOL. XXXVII.] PHILOSOPHICAL TRANSACTIONS. 457 



that which was farthest much stronger than that near which the tube was held. 

 About the middle of the line of communication they both attracted with equal 

 force. 



Some time after, at Mr. Wheler's, they made the following experiment, to 

 try whether the electric attraction be proportional to the quantity of matter in 

 bodies. — ^There were made two cubes of oak, about 6 inches square, the one 

 solid, the other hollow : these were suspended by 1 hair-lines, nearly after the 

 same manner as in the experiment abovementioned : the distance of the cubes 

 from each other was about 14 or 15 feet ; the line of communication being tied 

 to each hair-line, and the leaf-brass placed under the cubes, the tube was rubbed 

 and held over the middle of the line, and as near as could be guessed, at equal 

 distances from the cubes ; when both of them attracted and repelled the leaf- 

 brass at the same time, and to the same height : so that there seemed to be no 

 more attraction in the solid, than in the hollow cube ; yet Mr. Gray is apt to 

 think, that the electric effluvia pass through all the interior parts of the solid 

 cube, though no part but the surface attracts : for, from several experiments it 

 appears, that if any other body touch that which attracts, its attraction ceases 

 till the body be removed, and the other be again excited by the tube. 



The sequel of the experiments made at Mr. Godfrey's. 



Mr. Gray next went on with an experiment to see if the electric virtue might 

 not be conveyed to a rod, without inserting it into the bore of the tube, or 

 without touching the rod : which he found to succeed, by suspending the rod 

 either by lines of silk, or by pieces of horse-hair fishing lines, placing a ball of 

 cork on the lesser end of the rod. 



August 13, 1729, he took a large pole, 27 feet long, 2-i- inches diameter at 

 the great end, and about half an inch at the less end: it was that sort of wood 

 they call horse-beech, with the rind on. This was suspended by 2 hair-lines of 

 about 4-i- feet in length : the first line was about 2 feet from the great end of 

 the pole ; the other about 8 feet from the less end : so that the pole hung hori- 

 zontal. At the small end of the pole was suspended a ball of cork, about an 

 inch and a half in diameter, by a packthread about a foot long, and a small 

 leaden ball on the cork, to keep the packthread extended. Tlien the leaf-brass 

 being laid under the cork, the tube rubbed, and held near the great end of the 

 pole, the cork-ball attracted the leaf-brass strongly to the height of an inch, if 

 not more : then the leaf-brass being held under several parts of the pole, it was 

 attracted, as Mr. Godfrey observed, but not near so strongly as by the cork. 



About the beginning of September 1729, Mr. Gray made the following 

 experiment ; which shows that the electric effluvia will be carried in a circle, 

 and communicated from one circle to another. — There was taken a hoop, of 



VOL. VII. 3 N 



