The Doctor supposed that all the operations in electricity, depended upon one fluid, _sui generis_, extremely subtile and elastic.—That there subsists a very strong repulsion between the particles of this fluid, in regard to one another, and as strong an attraction, with regard to other matter.—Thus one quantity of electric matter will repel another quantity of the same, but will attract, and be attracted by, any terrestrial matter that happens to be near it. The pores of all bodies are supposed to be full of this subtile fluid; and when its equilibrium is not disturbed, that is, when there is neither more nor less of it in a body than its natural share, or than it is capable of retaining by its own attraction, the fluid does not manifest itself to our senses. The action of the rubber upon an electric disturbs this equilibrium, occasioning a redundancy of the fluid in one place, and a deficiency of it in another. This equilibrium being forcibly disturbed, the mutual repulsion of the particles of the fluid is necessarily exerted to restore it. If two bodies be both of them over-charged, the electric atmospheres repel one another, and both the bodies recede from each other, to places where the fluid is less dense.—For as there is supposed to be a mutual attraction between all bodies and the electric matter, such bodies as are electrified must go along with their atmospheres. If both bodies are exhausted of their natural share of this fluid, they are both attracted by the denser fluid, existing either in the atmosphere contiguous to them, or in other neighbouring bodies; which occasions them still to recede from one another, as if they were over-charged.