Mr. Grey continued to study electricity as long as he lived; and besides giving a set of fanciful experiments, by which he supposed he had discovered a perpetual attractive power in electrics, he, a little while before his death, entered on another course by which he hoped he should be able to astonish the world with a new sort of planetarium. “I have lately made (says he) several new experiments upon the projectile and pendulous motions of small bodies by electricity; by which small bodies may be made to move about large ones, either in circles or ellipses, and those either concentric or excentric to the centre of the large body about which they move, so as to make many revolutions about them. And this motion will constantly be the same way that the planets move round the sun, viz. from the right hand to the left, or from west to east. But these little planets, if I may so call them, move much faster in their apogean, than in the perigean part of their orbits; which is directly contrary to the motion of the planets round the sun.” The manner in which these experiments were made, as delivered by him on his death-bed to Dr. Mortimer, was as follows: “Place a small iron globe (said he) of an inch or an inch and a half in diameter, on the middle of a circular cake of rosin, seven or eight inches in diameter, greatly excited; and then a light body, suspended by a very fine thread, five or six inches long, held in the hand over the centre of the cake, will, of itself, begin to move in a circle round the iron globe, and constantly from west to east. If the globe is placed at any distance from the centre of the circular cake, it will describe an ellipse, 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 elliptical form, and the iron globe be placed in the centre of it, the light body will describe an elliptical orbit, of the same excentricity with the form of the cake. If the globe be placed in or near one of the foci of the elliptical cake, the light body will move much swifter in the apogee, than in the perigee of its orbit. If the iron globe is fixed on a pedestal an inch from the table, and a glass hoop, or a portion of a hollow glass cylinder excited, be placed round it, the light body will move as in the circumstance mentioned above, and with the same varieties.” He said, moreover, that the light body would make the same revolutions, only smaller, round the iron globe placed on the bare table, without any electrical substance to support it: but he acknowledged that he had not found the experiment succeed if the thread was supported by any thing but the human hand; though he imagined any other animal substance would have answered the purpose.