1 10 PHILOSOPHICAL TBANSACTIONS. [anNO 1735. 



Some Electrical Experiments intended to be communicated to the Royal Society, 

 by Mr. Stephen Gray, F. R. S. and taken from his Mouth by Cromwell Mor- 

 timer, M.D. R. S. Seer. Feb. 14, 1735-6, being the Day before he died, 

 N° 444, p. 400. 



Exper. 1. — Take a small iron globe, of an inch or inch and half diameter, 

 which set on the middle of a cake of rosin, of about 7 or 8 inches diameter, 

 having first excited the cake by gently rubbing it, clapping it three or four times 

 with the hands, or warming it a little before the fire. Then fasten a light 

 body, as a small piece of cork, or pith of elder, to an exceedingly fine thread, 

 5 or 6 inches long, which hold between the finger and thumb, exactly over the 

 globe, at such a height, that the cork, or other light body, may hang down 

 about the middle of the globe; this light body will of itself begin to move 

 round the iron globe, and that constantly from west to east, being the same 

 direction which the planets have in their orbits round the sun. If the cake of 

 rosin be circular, and the iron globe placed exactly in its centre, then the light 

 body will describe a circular orbit round the iron globe ; but if the iron globe 

 be placed at any distance from the centre of the circular cake, tlien the light 

 body will describe an elliptical orbit, which will have the same excentricity as 

 the distance of the globe from the centre of the cake. 



If the cake of rosin be of an elliptic form, and the iron globe be placed in its 

 centre, the light body will describe an elliptical orbit, of the same excentricity 

 as the form of the cake. 



If the iron globe be placed in or near one focus of the elliptical cake, the 

 light body will move much swifter in the apogee part of the orbit than in the 

 perige^ part, contrary to what is observed of the planets. 



Exper. 1. — Take the same, or such another iron globe, and having fastened 

 it on an iron pedestal about one inch high, set it on a table: then set round it 

 a glass hoop or portion of a hollow glass cylinder, of 7 or 8 inches diameter, 

 and 2 or 3 inches high: this hoop must be first excited by warming and gently 

 rubbing it; then hold the light body suspended as in the first experiment, and 

 it will of itself move round the iron globe from west to east, in a circular orbit, 

 if the hoop be circular and the globe stand over its centre, but in an elliptic 

 orbit, with the same excentricity, if the globe does not stand in the centre of 

 the hoop, as in the first experiment, when the globe does not stand on the 

 centre of the cake. 



Exper. 3. — ^Tbis same iron globe being set on the bare table, without either 

 the cake of rosin or the glass hoop, the small light body, being suspended as 



