APPENDIX TO THE PAPERS ON ELECTRICITY. No. I. WATSON'S ABSTRACT OF FRANKLIN'S ELECTRICAL EXPERIMENTS AND OBSERVATIONS. An Account of Mr. Benjamin Franklin's Treatise, lately published, entitled " Experiments and Observations on Electricity, made at Philadelphia in America;" by William Watson, F. R. S. READ AT THE ROYAL SOCIETY, JUNE 6TH, 1751. MR. FRANKLIN's Treatise, lately presented to the Royal Society, consists of four letters to his correspondent in England, and of another part, entitled "Opinions and Conjectures concerning the Properties and Effects of the Electrical Matter, arising from Experiments and Observations." The four letters, the last of which contains a new hypothesis for explaining the several phenomena of thunder-gusts, have, either in the whole or in part, been before communicated to the Royal Society. It remains, therefore, that I now only lay before the Society an account of the latter part of this treatise, as well as that of a letter intended to be added thereto by the author, but which arrived too late for publication with it, and was therefore communicated to the Society by our worthy brother, Mr. Peter Collinson. This ingenious author, from a great variety of curious and welladapted experiments, is of opinion, that the electrical matter consists of particles extremely subtile; since it can permeate common matter, even the densest metals, with such ease and freedom, as not to receive any perceptible resistance; and that, if any one should doubt, whether the electrical matter passes through the substance of bodies, or only over and along their surfaces, a shock from an electrified large glass jar, taken through his own body, will probably convince him. Electrical matter, according to our author, differs from common matter in this, that the parts of the latter mutually attract, and those of the former mutually repel, each other; hence the divergency in a stream of electrified effluvia.* But that, though the particles of electrical matter do repel each other, they are strongly attracted by all other matter. From these three things, viz. the extreme subtilty of the electrical matter, the mutual repulsion of its parts, and the strong attraction between them and other matter, arises this effect, that when a quantity of electrical matter is applied to a mass of common matter of any bigness or length within our observation (which has not already got its quantity), it is immediately and equally diffused through the whole. Thus common matter is a kind of sponge to the electrical fluid; and, as a sponge would receive no water, if the parts of water were not smaller than the pores of the sponge; and even then but slowly, if there was not a mutual attraction between those parts and the parts of the sponge; and would still imbibe it faster, if the mutual attraction among the parts of the water did not impede, some force being required to separate them; and fastest, if, instead of attrac tion, there were a mutual repulsion among those parts, which would act in conjunction with the attraction of the sponge; so is the case between the electrical and common matter. In common matter, indeed, there is generally as much of the electrical as it will contain within its substance; if more is added, it lies without upon the surface,† and forms what we call an electrical atmosphere, and then the body is said to be electrified. It is supposed, that all kinds of common matter do not attract and retain the electrical with equal force, for reasons to be given hereafter; and that those called electrics per se, as glass, &c., attract and retain it the strongest, and contain the greatest quantity. We know that the electrical fluid is in common matter, because we can pump it out by the globe or tube; and that common matter has near as much as it can contain, because, when we add a little more to any portion of it, the additional quantity does not enter, but forms an electrical atmosphere; and we know, that * As the electric stream is observed to diverge very little, when the experiment is made in vacuo, this appearance is more owing to the resistance of the atmosphere, than to any natural tendency in the electricity itself.-W. W. The author of this account is of opinion, that what is here added, lies not only without upon the surface, but penetrates with the same degree of density the whole mass of common matter upon which it is directed. common matter has not (generally) more than it can contain ; otherwise all loose portions of it would repel each other, as they constantly do when they have electric atmospheres. The form of the electrical atmosphere is that of the body which it surrounds. This shape may be rendered visible in a still air, by raising a smoke from dry resin dropped into a hot teaspoon under the electrified body, which will be attracted and spread itself equally on all sides, covering and concealing the body. And this form it takes, because it is attracted by all parts of the surface of the body, though it cannot enter the substance already replete. Without this attraction it would not remain round the body, but be dissipated in the air. The atmosphere of electrical particles surrounding an electrified sphere is not more disposed to leave it, or more easily drawn off from any one part of the sphere than from another, because it is equally attracted by every part. But that is not the case with bodies of any other figure. From a cube it is more easily drawn at the corners than at the plane sides, and so from the angles of a body of any other form, and still most easily from the angle that is most acute; and, for this reason, points have a property of drawing on, as well as throwing off, the electrical fluid, at greater distances than blunt bodies can. From various experiments recited in our author's treatise, to which the curious may have recourse, the preceding observations are deduced. You will observe how much they coincide with and support those which I some time since communicated to the Society upon the same subject. To give even the shortest account of all the experiments contained in Mr. Franklin's book, would exceed greatly the time allowed for these purposes by the Royal Society; I shall content myself, therefore, with laying a few of the most singular ones before you. The effects of lightning, and those of electricity, appear very similar. Lightning has often been known to strike people blind. A pigeon, struck dead to appearance by the electrical shock, recovering life, drooped several days, ate nothing, though crumbs were thrown to it, but declined and died. Mr. Franklin did not think of its being deprived of sight; but afterwards a pullet, struck dead in like manner, being recovered by repeatedly blowing into its lungs, when set down on the floor, ran headlong against the wall, and on examination appeared perfectly blind; hence he concluded, that the pigeon also had been absolutely blinded by the |