From the original accounts, as Dr. Priestley observes, could we not have repeated the experiment, we should have formed a very different idea of the electric shock to what it really is, even when given in greater strength than it could have been by those early experimenters. It was this experiment, however, that first made electri. city a subject of general curiosity. Every body was eager, not. withstanding the alarming reports that were spread of it, to feel the new sensation; and in the same year in which the experiment was first made at Leyden, numbers of persons, in almost every country in Europe, obtained a livelihood by going about and showing it.

The particulars, then, that we have enumerated may be said to have constituted the whole of the science of Electricity, in the shape in which it first presented itself to the notice of Dr. Franklin. In the way in which we have stated them, they are little more, the reader will observe, than a mass of seemingly unconnected facts, having, at first sight, no semblance whatever of being the results of a common principle, or of being reducible to any general and comprehensive system. It is true that a theory, that of M. Dufay, had been formed before this time to account for many of them, and also for others that we have not mentioned; but it does not appear that Franklin ever heard of it until he had formed his own, which is, at all events, entirely different; so that it is unnecessary for us to take it at all into account. We shall form a fair estimate of the amount and merits of Franklin's discoveries, by considering the facts we have mentioned, as really constituting the science in the state in which he found it.

It was in the year 1746, as he tells us himself in the narrative of his life, that, being at Boston, he met with a Dr. Spence, who had lately arrived from Scotland, and who showed him some electrical experiments. They were imperfectly performed, as the doctor was not very expert; "but being," says Franklin, " on a subject quite new to me, they equally surprised and pleased me. Soon after my return to Philadelphia, our Library Company received from Mr. Peter Collinson, F. R. S., of London, a present of a glass tube, with some account of the use of it in making such experiments. I eagerly seized the opportunity of repeating what I had seen at Boston; and, by much practice, acquired great readiness in performing those also which we had an account of from England, adding a number of new ones. I say much practice, for my house was continually full for some time, with persons who came to see these new wonders. To divide a little this encumbrance among my friends, I caused a number of similar tubes to be blown in our glass house, with which they furnished themselves, so that we had at length several performers." The newly discovered and extraor

dinary phenomena exhibited by the Leyden phial of course very early engaged his attention in pursuing these interesting experiments; and his inquisitive mind immediately set itself to work to find out the reason of such strange effects, which still astonished and perplexed the ablest philosophers of Europe. Out of his speculations arose the ingenious and beautiful theory of the action of the electric influence which is known by his name: and which has ever since been received by the greater number of philosophers as the best, because the simplest and most complete, demonstration of the phenomena that has yet been given to the world.

Dr. Franklin's earliest inquiries were directed to ascertain the source of the electricity which friction had the effect of at least rendering manifest in the glass cylinder, or other electric. The question was, whether this virtue was created by the friction in the electric, or only thereby communicated to it from other bodies. In order to determine this point, he resorted to the very simple experiment of endeavoring to electrify himself; that is to say, having insulated himself, and excited the cylinder by rubbing it with his hand, he then drew off its electricity from it in the usual manner into his own body. But he found that he was not thereby electrified at all, as he would have been by doing the same thing, had the friction been applied by another person. No spark could be obtained from him, after the operation, by the presentment of a conductor; nor did he exhibit on such bodies as were brought near him any of the other usual evidences of being charged with

electricity.

If the electricity had been created in the electric by the friction, it was impossible to conceive why the person who drew it off should not have been electrified in this case, just as he would have been had another person acted as the rubber. The result evidently indicated that the friction had effected a change upon the person who had performed that operation, as well as upon the cylinder, since it had rendered him incapable of being electrified by a process by which, in other circumstances, he would have been so. It was plain, in short, that the electricity had passed, in the first instance, out of his body into the cylinder; which, therefore, in communicating it to him in the second instance, only gave him back what it had received, and, instead of electrifying him, merely re. stored him to his usual state-to that in which he had been before the experiment was begun.

This accordingly was the conclusion to which Franklin came; but, to confirm it, he next insulated two individuals, one of whom he made to rub the cylinder, while the other drew the electricity from it. In this case, it was not the latter merely that was

affected; both were electrified. The one had given out as much electricity to the cylinder in rubbing it, as the other had drawn from it. To prove this still farther, he made them touch one another, when both were instantly restored to their usual state, the redundant electricity thrown off by the one exactly making up the deficiency of the other. The spark produced by their contact was also, as was to have been expected, greater than that which took place when either of them was touched by any third person who had not been electrified.

Proceeding upon the inferences which these results seemed so evidently to indicate, Franklin constructed the general outlines of his theory. Every body in nature he considered to have its natural quantity of electricity, which may, however, be either diminished, by part of it being given out to another body, as that of the rubber, in the operation of the electrical machine, is given out to the cylinder; or increased, as when the body is made to receive the electricity from the cylinder. In the one case he regarded the body as negatively, in the other as positively, electrified. one case it had less, in the other more, than its natural quantity of electricity: in either, therefore, supposing it to be composed of electricity and common matter, the usual equilibrium or balance between its two constituent ingredients was, for the time, upset or destroyed.

In the

But how should this produce the different effects which are observed to result from the action of electrified bodies? How is the mere circumstance of the overthrow of the customary equilibrium between the electricity and the matter of a body to be made to account for its attraction and repulsion of other bodies, and for the extraordinary phenomena presented by the Leyden phial? The Franklinian theory answers these questions with great ease and completeness.

The fundamental law of the electric fluid, according to this theory, is, that its particles attract matter, and repel one another. To this we must add a similar law with regard to the particles of matter, namely, that they repel each other, as well as attract electricity. This latter consideration was somewhat unaccountably overlooked by Franklin; but was afterwards introduced by Mr. Apinus, of Petersburg, and the late celebrated Mr. Cavendish, in their more elaborate expositions of his theory of the electrical action. Let us now apply these two simple principles to the explanation of the facts we have already mentioned.

In the first place, when two bodies are in their ordinary or natural state, the quantity of matter is an exact balance for the quantity of electricity in each, and there is accordingly no tendency

of the fluid to escape; no spark will take place between two such bodies when they are brought into contact. Nor will they either attract or repel each other, because the attractive and repulsive forces operating between them are exactly balanced, the two attractions of the electricity in the first for the matter in the second, and of the electricity in the second for the matter in the first, being opposed by the two repulsions of the electricity in the first for the electricity in the second, and of the matter in the first for the matter in the second. They, therefore, produce no effect upon each other whatever.

Let

But let us next suppose that one of the bodies is an electric which has been excited in the usual way by friction, a stick of wax, or a glass cylinder, for example, which has been rubbed with the hand, or a piece of dry silk. In this case, the body in question has received an addition to its natural quantity of electricity, which addition, accordingly, it will most readily part with whenever it is brought into contact with a conductor. But this is not all. us see how it will act, according to the law that has been stated, upon the other body, which we shall suppose to be in its natural state, when they are brought near each other. First, from the repulsive tendency of the electric particles, the extra electricity in the excited body will drive away a portion of the electricity of the other from its nearest end, which will thus become negatively electrified, or will consist of more matter than is necessary to balance its electricity. In this state of things, what are the attractive and repulsive forces operating between the two bodies, the one, be it remembered, having an excess of electricity, and the other an excess of matter? There are, in fact, five attractive forces opposed by only four repulsive; the former being those of the matter in the first body for the electricity in the second, of the balanced electricity in the first for the balanced matter in the second, of the same for the extra matter in the second, together with the two of the extra electricity in the first for the same two quantities of matter; and the latter being those of the matter in the first for the balanced matter in the second, of the same for the extra matter in the second, together with those of the electricity in the second both for the balanced and the extra electricity in the first. The two bodies, therefore, ought to meet, as we find they actually do. But no sooner do they meet than the extra electricity of the first, attracted by the matter of the second, flows over partly to it; and both bodies become positively electrified; that is to say, each contains a quantity of electricity beyond that which its matter is capable of balancing. It will be found, upon examination, that we have now four powers of attraction opposed by five of repul

sion; the former being those of the matter in each body for the two electricities in the other, the latter those exerted by each of the electricities in the one against both the electricities of the other, together with that of the matter in the one for the matter in the other. The bodies now accordingly should repel each other, just as we find to be the fact. Of course the same reasoning applies to the case of a neutral body, and any other containing a superabundance of electricity, whether it be an electric or no, and in whatever way its electricity may have been communicated to it. We may add that there is no case of attraction or repulsion between two bodies, in which the results indicated by the theory do not coincide with those of observation as exactly as in this.

We now come to the phenomena of the Leyden phial. The two bodies upon which we are here to fix our attention are the interior and exterior coatings, which, before the process of charging has commenced, are of course in their natural state, each having exactly that quantity of electricity which its matter is able to balance, and neither therefore exerting any effect whatever upon the other. But no sooner has the interior coating received an additional portion of electricity from the prime conductor, with which the reader will remember it is in communication, than, being now positively electrified, it repels a corresponding portion of its electricity from the exterior coating, which therefore be comes negatively electrified. As the operation goes on, both these effects increase, till at last the superabundance of electricity in the one surface, and its deficiency in the other, reach the limit to which it is wished to carry them. All this while, it will be remarked, the former is prevented from giving out its superfluity to the latter by the interposition of the glass, which is a non-conductor, and the uncovered space which had been left on both sides around the lip of the vessel. If the charge were made too high, however, even these obstacles would be overcome, and the unbalanced electricity of the interior coating, finding no easier vent, would at last rush through the glass to the unsaturated matter on its opposite surface, probably shattering it to pieces in its progress. But, to effect a discharge in the usual manner, a communication must be established by means of a good conductor between the two surfaces, before this extreme limit be reached. If either a rod of metal, for example, or the human body, be employed for this purpose, the fluid from the interior coating will instantly rush along the road made for it, occasioning a pretty loud report, and, in the latter case, a severe shock, by the rapidity of its passage. Both coatings will, in consequence, be immediately restored to

their natural state.