"Another from Cicero:—

"'O vitæ Philosophia dux! O virtutum indagatrix expultrixque vitiorum! Unus dies ex præceptis tuis actus, peccanti immortalitati est anteponendus.'

"Another from the Proverbs of Solomon, speaking of wisdom and virtue:—

"'Length of days is in her right hand; and in her left hand riches and honour. Her ways are ways of pleasantness, and all her paths are peace.'

"And conceiving God to be the fountain of wisdom, I thought it right and necessary to solicit His assistance for obtaining it; to this end I formed the following little prayer, which was prefixed to my tables of examination, for daily use:—

"'O powerful Goodness! bountiful Father! merciful Guide! increase in me that wisdom which discovers my truest interest. Strengthen my resolutions to perform what that wisdom dictates. Accept my kind offices to Thy other children as the only return in my power for Thy continual favours to me.'

"I used also sometimes a little prayer which I took from Thomson's Poems, viz.:—

The senses in which Franklin's thirteen virtues were to be understood were explained by short precepts which followed them in his list. The list was as follows:—

"Imitate Jesus and Socrates."

The last of these was added to the list at the suggestion of a Quaker friend. Franklin claims to have acquired a good deal of the appearance of it, but concluded that in reality there was no passion so hard to subdue as pride. "For even if I could conceive that I had completely overcome it, I should probably be proud of my humility." The virtue which gave him most trouble, however, was order, and this he never acquired.

In 1732 appeared the first copy of "Poor Richard's Almanack." This was prepared, printed, and published by Franklin for about twenty-five years in succession, and nearly ten thousand copies were sold annually. Besides the usual astronomical information, it contained a collection of entertaining anecdotes, verses, jests, etc., while the "little spaces that occurred between the remarkable events in the calendar" were filled with proverbial sayings, inculcating industry and frugality as helps to virtue. These sayings were collected and prefixed to the almanack of 1757, whence they were copied into the American newspapers, and afterwards reprinted as a broad-sheet in England and in France.

In 1733 Franklin commenced studying modern languages, and acquired sufficient knowledge of French, Italian, and Spanish to be able to read books in those languages. In 1736 he was chosen Clerk to the General Assembly, an office to which he was annually re-elected until he became a member of the Assembly about 1750. There was one member who, on the second occasion of his election, made a long speech against him. Franklin determined to secure the friendship of this member. Accordingly he wrote to him to request the loan of a very scarce and curious book which was in his library. The book was lent and returned in about a week, with a note of thanks. The member ever after manifested a readiness to serve Franklin, and they became great friends—"Another instance of the truth of an old maxim I had learned, which says, 'He that has once done you a kindness will be more ready to do you another than he whom you yourself have obliged.' And it shows how much more profitable it is prudently to remove, than to resent, return, and continue inimical proceedings."

In 1737 Franklin was appointed Deputy-Postmaster-General for Pennsylvania. He was afterwards made Postmaster-General of the Colonies. He read a paper in the Junto on the organization of the City watch, and the propriety of rating the inhabitants on the value of their premises in order to support the same. The subject was also discussed in the other clubs which had sprung from the Junto, and thus the way was prepared for the law which a few years afterwards carried Franklin's proposals into effect. His next scheme was the formation of a fire brigade, in which he met with his usual success, and other clubs followed, until most of the men of property in the city were members of one club or another. The original brigade, known as the Union Fire Company, was formed December 7, 1736. It was in active service in 1791.

Franklin founded the American Philosophical Society in 1743. The head-quarters of the society were fixed in Philadelphia, where it was arranged that there should always be at least seven members, viz. a physician, a botanist, a mathematician, a chemist, a mechanician, a geographer, and a general natural philosopher, besides a president, treasurer, and secretary. The other members might be resident in any part of America. Correspondence was to be kept up with the Royal Society of London and the Dublin Society, and abstracts of the communications were to be sent quarterly to all the members. Franklin became the first secretary.

Spain, having been for some years at war with England, was joined at length by France. This threatened danger to the American colonies, as France then held Canada, and no organization for their defence existed. Franklin published a pamphlet entitled "Plain Truth," setting forth the unarmed condition of the colonies, and recommending the formation of a volunteer force for defensive purposes. The pamphlet excited much attention. A public meeting was held and addressed by Franklin; at this meeting twelve hundred joined the association. At length the number of members enrolled exceeded ten thousand. These all provided themselves with arms, formed regiments and companies, elected their own officers, and attended once a week for military drill. Franklin was elected colonel of the Philadelphia Regiment, but declined the appointment, and served as a private soldier. The provision of war material was a difficulty with the Assembly, which consisted largely of Quakers, who, though they appeared privately to be willing that the country should be put in a state of defence, hesitated to vote in opposition to their peace principles. Hence it was that, when the Government of New England asked a grant of gunpowder from Pennsylvania, the Assembly voted £3000 "for the purchasing of bread, flour, wheat, or other grain." Pebble-powder was not then in use. When it was proposed to devote £60, which was a balance in the hands of the Union Fire Company, as a contribution towards the erection of a battery below the town, Franklin suggested that it should be proposed that a fire-engine be purchased with the money, and that the committee should "buy a great gun, which is certainly a fire-engine."

The "Pennsylvania fireplace" was invented in 1742. A patent was offered to Franklin by the Governor of Pennsylvania, but he declined it on the principle "that, as we enjoy great advantages from the inventions of others, we should be glad of an opportunity to serve others by any invention of ours; and this we should do freely and generously." An ironmonger in London made slight alterations, which were not improvements, in the design, and took out a patent for the fireplace, whereby he made a "small fortune." Franklin never contested the patent, "having no desire of profiting by patents himself," and "hating disputes." This fireplace was designed to burn wood, but, unlike the German stoves, it was completely open in front, though enclosed at the sides and top. An air-chamber was formed in the middle of the stove, so arranged that, while the burning wood was in contact with the front of the chamber, the flame passed above and behind it on its way to the flue. Through this chamber a constant current of air passed, entering the room heated, but not contaminated, by the products of combustion. In this way the stove furnished a constant supply of fresh warm air to the room, while it possessed all the advantages of an open fireplace. Subsequently Franklin contrived a special fireplace for the combustion of coal. In the scientific thought which he devoted to the requirements of the domestic economist, as in very many other particulars, Franklin strongly reminds us of Count Rumford.

The next important enterprise which Franklin undertook, partly through the medium of the Junto, was to establish an academy which soon developed into the University of Philadelphia. The members of the club having taken up the subject, the next step was to enlist the sympathy of a wider constituency, and this Franklin effected, in his usual way, by the publication of a pamphlet. He then set on foot a subscription, the payments to extend over five years, and thereby obtained about £5000. A house was taken and schools opened in 1749. The classes soon became too large for the house, and the trustees of the academy then took over a large building, or "tabernacle," which had been erected for George Whitefield when he was preaching in Philadelphia. The hall was divided into stories, and at a very small expense adapted to the requirements of the classes. Franklin, having taken a partner in his printing business, took the oversight of the work. Afterwards the funds were increased by English subscriptions, by a grant from the Assembly, and by gifts of land from the proprietaries; and thus was established the University of Philadelphia.

Having practically retired from business, Franklin intended to devote himself to philosophical studies, having commenced his electrical researches some time before in conjunction with the other members of the Library Company. Public business, however, crowded upon him. He was elected a member of the Assembly, a councillor and afterwards an alderman of the city, and by the governor was made a justice of the peace. As a member of the Assembly, he was largely concerned in providing the means for the erection of a hospital, and in arranging for the paving and cleansing of the streets of the city. In 1753 he was appointed, in conjunction with Mr. Hunter, Postmaster-General of America. The post-office of the colonies had previously been conducted at a loss. In a few years, under Franklin's management, it not only paid the stipends of himself and Mr. Hunter, but yielded a considerable revenue to the Crown. But it was not only in the conduct of public business that Franklin's merits were recognized. By this time he had secured his reputation as an electrician, and both Yale College and Cambridge University (New England) conferred on him the honorary degree of Master of Arts. In the same year that he was made Postmaster-General of America he was awarded the Copley Medal and elected a Fellow of the Royal Society of London, the usual fees being remitted in his case.

Before his election as member, Franklin had for several years held the appointment of Clerk to the Assembly, and he used to relieve the dulness of the debates by amusing himself in the construction of magic circles and squares, and "acquired such a knack at it" that he could "fill the cells of any magic square of reasonable size with a series of numbers as fast as" he "could write them." Many years afterwards Mr. Logan showed Franklin a French folio volume filled with magic squares, and afterwards a magic "square of 16," which Mr. Logan thought must have been a work of great labour, though it possessed only the common properties of making 2056 in every row, horizontal, vertical, and diagonal. During the evening Franklin made the square shown on the opposite page. "This I sent to our friend the next morning, who, after some days, sent it back in a letter, with these words: 'I return to thee thy astonishing and most stupendous piece of the magical square, in which——;' but the compliment is too extravagant, and therefore, for his sake as well as my own, I ought not to repeat it. Nor is it necessary; for I make no question that you will readily allow this square of 16 to be the most magically magical of any magic square ever made by any magician."

The square has the following properties:—Every straight row of sixteen numbers, whether vertical, horizontal, or diagonal, makes 2056.

Every bent row of sixteen numbers, as shown by the diagonal lines in the figure, makes 2056.

If a square hole be cut in a piece of paper, so as to show through it just sixteen of the little squares, and the paper be laid on the magic square, then, wherever the paper is placed, the sum of the sixteen numbers visible through the hole will be 2056.

In 1754 war with France appeared to be again imminent, and a Congress of Commissioners from the several colonies was arranged for. Of course, Franklin was one of the representatives of Pennsylvania, and was also one of the members who independently drew up a plan for the union of all the colonies under one government, for defensive and other general purposes, and his was the plan finally approved by Congress for the union, though it was not accepted by the Assemblies or by the English Government, being regarded by the former as having too much of the prerogative in it, by the latter as being too democratic. Franklin wrote respecting this scheme: "The different and contrary reasons of dislike to my plan makes me suspect that it was really the true medium; and I am still of opinion that it would have been happy for both sides of the water if it had been adopted. The colonies, so united, would have been sufficiently strong to have defended themselves; there would then have been no need of troops from England; of course, the subsequent pretence for taxing America, and the bloody contest it occasioned, would have been avoided."

With this war against France began the struggle of the Assemblies and the proprietaries on the question of taxing the estates of the latter. The governors received strict instructions to approve no bills for the raising of money for the purposes of defence, unless the estates of the proprietaries were specially exempted from the tax. The Assembly of Pennsylvania resolved to contribute £10,000 to assist the Government of Massachusetts Bay in an attack upon Crown Point, but the governor refused his assent to the bill for raising the money. At this juncture Franklin proposed a scheme by which the money could be raised without the consent of the governor. His plan was successful, and the difficulty was surmounted for the time, but was destined to recur again and again during the progress of the war.

The British Government, not approving of the scheme of union, whereby the colonies might have defended themselves, sent General Braddock to Virginia, with two regiments of regular troops. On their arrival they found it impossible to obtain waggons for the conveyance of their baggage, and the general commissioned Franklin to provide them in Pennsylvania. By giving his private bond for their safety, Franklin succeeded in engaging one hundred and fifty four-horse waggons, and two hundred and fifty-nine pack-horses. His modest warnings against Indian ambuscades were disregarded by the general, the little army was cut to pieces, and the remainder took to flight, sacrificing the whole of their baggage and stores. Franklin was never fully recouped by the British Government for the payments he had to make on account of provisions which the general had instructed him to procure for the use of the army.

After this, Franklin appeared for some time in a purely military capacity, having yielded to the governor's persuasions to undertake the defence of the north-western frontier, to raise troops, and to build a line of forts. After building and manning three wooden forts, he was recalled by the Assembly, whose relations with the governor had become more and more strained. At length the Assembly determined to send Franklin to England, to present a petition to the king respecting the conduct of the proprietaries, viz. Richard and Thomas Penn, the successors of William Penn. A bill had been framed by the House to provide £60,000 for the king's use in the defence of the province. This the governor refused to pass, because the proprietary estates were not exempted from the taxation. The petition to the king was drawn up, and Franklin's baggage was on board the ship which was to convey him to England, when General Lord Loudon endeavoured to make an arrangement between the parties. The governor pleaded his instructions, and the bond he had given for carrying them out, and the Assembly was prevailed upon to reconstruct the bill in accordance with the governor's wishes. This was done under protest; in the mean time Franklin's ship had sailed, carrying his baggage. After a great deal of unnecessary delay on account of the general's inability to decide upon the despatch of the packet-boats, Franklin at last got away from New York, and, having narrowly escaped shipwreck off Falmouth, he reached London on July 27, 1757.

On arriving in London, Franklin was introduced to Lord Granville, who told him that the king's instructions were laws in the colonies. Franklin replied that he had always understood that the Assemblies made the laws, which then only required the king's consent. "I recollected that, about twenty years before, a clause in a bill brought into Parliament by the Ministry had proposed to make the king's instructions laws in the colonies, but the clause was thrown out by the Commons, for which we adored them as our friends and the friends of liberty, till, by their conduct towards us in 1765, it seem'd that they had refus'd that point of sovereignty to the king only that they might reserve it for themselves." A meeting was shortly afterwards arranged between Franklin and the proprietaries at Mr. T. Penn's house; but their views were so discordant that, after some discussion, Franklin was requested to give them in writing the heads of his complaints, and the whole question was submitted to the opinion of the attorney- and solicitor-general. It was nearly a year before this opinion was given. The proprietaries then communicated directly with the Assembly, but in the mean while Governor Denny had consented to a bill for raising £100,000 for the king's use, in which it was provided that the proprietary estates should be taxed with the others. When this bill reached England, the proprietaries determined to oppose its receiving the royal assent. Franklin engaged counsel on behalf of the Assembly, and on his undertaking that the assessment should be fairly made between the estates of the proprietaries and others, the bill was allowed to pass.

By this time Franklin's career as a scientific investigator was practically at an end. Political business almost completely occupied his attention, and in one sense the diplomatist replaced the philosopher. His public scientific career was of short duration. It may be said to have begun in 1746, when Mr. Peter Collinson presented an "electrical tube" to the Library Company in Philadelphia, which was some time after followed by a present of a complete set of electrical apparatus from the proprietaries, but by 1755 Franklin's time was so much taken up by public business that there was very little opportunity for experimental work. Throughout his life he frequently expressed in his letters his strong desire to return to philosophy, but the opportunity never came, and when, at the age of eighty-two, he was liberated from public duty, his strength was insufficient to enable him to complete even his autobiography.

It was on a visit to Boston in 1746 that Franklin met with Dr. Spence, a Scotchman, who exhibited some electrical experiments. Soon after his return to Philadelphia the tube arrived from Mr. Collinson, and Franklin acquired considerable dexterity in its use. His house was continually full of visitors, who came to see the experiments, and, to relieve the pressure upon his time, he had a number of similar tubes blown at the glass-house, and these he distributed to his friends, so that there were soon a number of "performers" in Philadelphia. One of these was Mr. Kinnersley, who, having no other employment, was induced by Franklin to become an itinerant lecturer. Franklin drew up a scheme for the lectures, and Kinnersley obtained several well-constructed instruments from Franklin's rough and home-made models. Kinnersley and Franklin appear to have worked together a good deal, and when Kinnersley was travelling on his lecture tour, each communicated to the other the results of his experiments. Franklin sent his papers to Mr. Collinson, who presented them to the Royal Society, but they were not at first judged worthy of a place in the "Transactions." The paper on the identity of lightning and electricity was sent to Dr. Mitchell, who read it before the Royal Society, when it "was laughed at by the connoisseurs." The papers were subsequently published in a pamphlet, but did not at first receive much attention in England. On the recommendation of Count de Buffon, they were translated into French. The Abbé Nollet, who had previously published a theory of his own respecting electricity, wrote and published a volume of letters defending his theory, and denying the accuracy of some of Franklin's experimental results. To these letters Franklin made no reply, but they were answered by M. le Roy. M. de Lor undertook to repeat in Paris all Franklin's experiments, and they were performed before the king and court. Not content with the experiments which Franklin had actually performed, he tried those which had been only suggested, and so was the first to obtain electricity from the clouds by means of the pointed rod. This experiment produced a great sensation everywhere, and was afterwards repeated by Franklin at Philadelphia. Franklin's papers were translated into Italian, German, and Latin; his theory met with all but universal acceptance, and great surprise was expressed that his papers had excited so little interest in England. Dr. Watson then drew up a summary of all Franklin's papers, and this was published in the "Philosophical Transactions;" Mr. Canton verified the experiment of procuring electricity from the clouds by means of a pointed rod, and the Royal Society awarded to Franklin the Copley Medal for 1753, which was conveyed to him by Governor Denny.

We must now give a short account of Franklin's contributions to electrical science.

"The first is the wonderful effect of pointed bodies, both in drawing off and throwing off the electrical fire."

It will be observed that this statement is made in the language of the one-fluid theory, of which Franklin may be regarded as the author. This theory will be again referred to presently. Franklin electrified a cannon-ball so that it repelled a cork. On bringing near it the point of a bodkin, the repulsion disappeared. A blunt body had to be brought near enough for a spark to pass in order to produce the same effect. "To prove that the electrical fire is drawn off by the point, if you take the blade of the bodkin out of the wooden handle, and fix it in a stick of sealing-wax, and then present it at the distance aforesaid, or if you bring it very near, no such effect follows; but sliding one finger along the wax till you touch the blade, and the ball flies to the shot immediately. If you present the point in the dark, you will see, sometimes at a foot distance or more, a light gather upon it like that of a fire-fly or glow-worm; the less sharp the point, the nearer you must bring it to observe the light; and at whatever distance you see the light, you may draw off the electrical fire, and destroy the repelling."

By laying a needle upon the shot, Franklin showed "that points will throw off as well as draw off the electrical fire." A candle-flame was found to be equally efficient with a sharp point in drawing off the electricity from a charged conductor. The effect of the candle-flame Franklin accounted for by supposing the particles separated from the candle to be first "attracted and then repelled, carrying off the electric matter with them." The effect of points is a direct consequence of the law of electrical repulsion. When a conductor is electrified, the density of the electricity is greatest where the curvature is greatest. Thus, if a number of spheres are electrified from the same source, the density of the electricity on the different spheres will vary inversely as their diameters. The force tending to drive the electricity off a conductor is everywhere proportional to the density, and hence in the case of the spheres will be greatest for the smallest sphere. On this principle, the density of electricity on a perfectly sharp point, if such could exist, on a charged conductor, would be infinite and the force tending to drive it off would be infinite also. Hence a moderately sharp point is sufficient to dissipate the electricity from a highly charged conductor, or to neutralize it if the point is connected to earth and brought near the conductor so as to be electrified by induction.

Franklin next found that, if the person rubbing the electric tube stood upon a cake of resin, and the person taking the charge from the tube stood also on an insulating stand, a stronger spark would pass between these two persons than between either of them and the earth; that, after the spark had passed, neither person was electrified, though each had appeared electrified before. These experiments suggested the idea of positive and negative electrification; and Franklin, regarding the electric fluid as corresponding to positive electrification, remarked that "you may circulate it as Mr. Watson has shown; you may also accumulate or subtract it upon or from any body, as you connect that body with the rubber or with the receiver, the common stock being cut off." Thus Franklin regarded electricity as a fluid, of which everything in its normal state possesses a certain amount; that, by appropriate means, some of the fluid may be removed from one body and given to another. The former is then electrified negatively, the latter positively, and all processes by which bodies are electrified consist in the removal of electricity from one body or system and giving it to another. He regarded the electric fluid as repelling itself and attracting matter. Æpinus afterwards added the supposition that matter, when devoid of electricity, is self-repulsive, and thus completed the "one-fluid theory," and accounted for the repulsion observed between negatively electrified bodies.

It had been usual to employ water for the interior armatures of Leyden jars, or phials, as they were then generally called. Franklin substituted granulated lead for the water, thereby improving the insulation by keeping the glass dry. With these phials he contrived many ingenious experiments, and imitated lightning by discharging them through the gilding of a mirror or the gold lines on the cover of a book. He found that the inner and outer armatures of his Leyden jars were oppositely electrified. "Here we have a bottle containing at the same time a plenum of electrical fire and a vacuum of the same fire; and yet the equilibrium cannot be restored between them but by a communication without! though the plenum presses violently to expand, and the hungry vacuum seems to attract as violently in order to be filled." The charging of Leyden jars by cascade, that is by insulating all the jars except the last, connecting the outer armature of the first with the inner armature of the second, and so on throughout the series, was well understood by Franklin, and he knew too that by this method the extent to which each jar could be charged from a given source varied inversely as the number of jars. The discharge of the Leyden jar by alternate contacts was also carried out by him; and he found that, if the jar is first placed on an insulating stand, it may be held by the hook (or knob) without discharging it. Franklin, in fact, appears to have known almost as much about the Leyden jar as is known to-day. He found that, when the armatures were removed from a jar, no discharge would pass between them, but when a fresh pair of armatures were supplied to the glass, the jar could be discharged. "We are of opinion that there is really no more electrical fire in the phial after what is called its charging than before, nor less after its discharging; excepting only the small spark that might be given to and taken from the non-electric matter, if separated from the bottle, which spark may not be equal to a five-hundredth part of what is called the explosion.

"The phial will not suffer what is called a charging unless as much fire can go out of it one way as is thrown in by another.

"When a bottle is charged in the common way, its inside and outside surfaces stand ready, the one to give fire by the hook, the other to receive it by the coating; the one is full and ready to throw out, the other empty and extremely hungry; yet, as the first will not give out unless the other can at the same time receive in, so neither will the latter receive in unless the first can at the same time give out. When both can be done at once, it is done with inconceivable quickness and violence."

Then follows a very beautiful illustration of the condition of the glass in the Leyden jar.

"So a straight spring (though the comparison does not agree in every particular), when forcibly bent, must, to restore itself, contract that side which in the bending was extended, and extend that which was contracted; if either of these two operations be hindered, the other cannot be done.

"Glass, in like manner, has, within its substance, always the same quantity of electrical fire, and that a very great quantity in proportion to the mass of the glass, as shall be shown hereafter.

"This quantity proportioned to the glass it strongly and obstinately retains, and will have neither more nor less, though it will suffer a change to be made in its parts and situation; i.e. we may take away part of it from one of the sides, provided we throw an equal quantity into the other."

"The whole force of the bottle, and power of giving a shock, is in the glass itself; the non-electrics in contact with the two surfaces serving only to give and receive to and from the several parts of the glass, that is, to give on one side and take away from the other."

All these statements were, as far as possible, fully substantiated by experiment. They are perfectly consistent with the views held by Cavendish and by Clerk Maxwell, and, though the phraseology is not that of the modern text-books, the statements themselves can hardly be improved upon to-day.

One of Franklin's early contrivances was an electro-motor, which was driven by the alternate electrical attraction and repulsion of leaden bullets which discharged Leyden jars by alternate contacts. Franklin concluded his account of these experiments as follows:—

Chagrined a little that we have been hitherto able to produce nothing in this way of use to mankind, and the hot weather coming on, when electrical experiments are not so agreeable, it is proposed to put an end to them for this season, somewhat humorously, in a party of pleasure, on the banks of Skuylkil. Spirits, at the same time, are to be fired by a spark sent from side to side through the river, without any other conductor than the water—an experiment which we some time since performed, to the amazement of many. A turkey is to be killed for our dinner by the electrical shock, and roasted by the electrical jack before a fire kindled by the electrified bottle, when the healths of all the famous electricians in England, Holland, France, and Germany, are to be drunk in electrified bumpers, under the discharge of guns from the electrical battery.

Franklin's electrical battery consisted of eleven large panes of glass coated on each side with sheet lead. The electrified bumper was a thin tumbler nearly filled with wine and electrified as a Leyden jar, so as to give a shock through the lips.

Franklin's theory of the manner in which thunder-clouds become electrified he found to be not consistent with his subsequent experiments. In the paper which he wrote explaining this theory, however, he shows some knowledge of the effects of bringing conductors into contact in diminishing their capacity. He states that two gun-barrels electrified equally and then united, will give a spark at a greater distance than one alone. Hence he asks, "To what a great distance may ten thousand acres of electrified cloud strike and give its fire, and how loud must be that crack?

"An electrical spark, drawn from an irregular body at some distance, is scarcely ever straight, but shows crooked and waving in the air. So do the flashes of lightning, the clouds being very irregular bodies.

"As electrified clouds pass over a country, high hills and high trees, lofty towers, spires, masts of ships, chimneys, etc., as so many prominences and points, draw the electrical fire, and the whole cloud discharges there.

"Dangerous, therefore, is it to take shelter under a tree during a thunder-gust. It has been fatal to many, both men and beasts.

"It is safer to be in the open field for another reason. When the clothes are wet, if a flash in its way to the ground should strike your head, it may run in the water over the surface of your body; whereas, if your clothes were dry, it would go through the body, because the blood and other humours, containing so much water, are more ready conductors.

"Hence a wet rat cannot be killed by the exploding electrical bottle [a quart jar], while a dry rat may."

In the above quotations we see, so to speak, the germ of the lightning-rod. This was developed in a letter addressed to Mr. Collinson, and dated July 29, 1750. The following quotations will give an idea of its contents:—

"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.[1]

"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.

"Common matter is a kind of sponge to the electrical fluid.

"We know that the electrical fluid is in common matter, because we can pump it out by the globe or tube. We know 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."

To illustrate the action of a lightning-conductor on a thunder-cloud, Franklin suspended from the ceiling a pair of scales by a twisted string so that the beam revolved. Upon the floor, in such a position that the scale-pans passed over it, he placed a blunt steel punch. The scale-pans were suspended by silk threads, and one of them electrified. When this passed over the punch it dipped towards it, and sometimes discharged into it by a spark. When a needle was placed with its point uppermost by the side of the punch, no attraction was apparent, for the needle discharged the scale-pan before it came near.

"Now, if the fire of electricity and that of lightning be the same, as I have endeavoured to show at large in a former paper ... these scales may represent electrified clouds.... The horizontal motion of the scales over the floor may represent the motion of the clouds over the earth, and the erect iron punch a hill or high building; and then we see how electrified clouds, passing over hills or high buildings at too great a height to strike, may be attracted lower till within their striking distance; and lastly, if a needle fixed on the punch, with its point upright, or even on the floor below the punch, will draw the fire from the scale silently at a much greater than the striking distance, and so prevent its descending towards the punch; or if in its course it would have come nigh enough to strike, yet, being first deprived of its fire, it cannot, and the punch is thereby secured from its stroke;—I say, if these things are so, may not the knowledge of this power of points be of use to mankind, in preserving houses, churches, ships, etc., from the stroke of the lightning, by directing us to fix, on the highest parts of those edifices, upright rods of iron made sharp as a needle, and gilt to prevent rusting, and from the foot of those rods a wire down the outside of the building into the ground, or down round one of the shrouds of a ship, and down her side till it reaches the water? Would not these pointed rods probably draw the electrical fire silently out of a cloud before it came nigh enough to strike, and thereby secure us from that most sudden and terrible mischief?"

Franklin goes on to suggest the possibility of obtaining electricity from the clouds by means of a pointed rod fixed on the top of a high building and insulated. Such a rod he afterwards erected in his own house. Another rod connected to the earth he brought within six inches of it, and, attaching a small bell to each rod, he suspended a little ball or clapper by a silk thread, so that it could strike either bell when attracted to it. On the approach of a thunder-cloud, and occasionally when no clouds were near, the bells would ring, indicating that the rod had become strongly electrified. On one occasion Franklin was disturbed by a loud noise, and, coming out of his bedroom, he found an apparently continuous and very luminous discharge taking place between the bells, forming a stream of fire about as large as a pencil.

A very pretty experiment of Franklin's was that of the golden fish. A small piece of gold-leaf is cut into a quadrilateral having one of its angles about 150°, the opposite angle about 30°, and the other two right angles. "If you take it by the tail, and hold it at a foot or greater horizontal distance from the prime conductor, it will, when let go, fly to it with a brisk but wavering motion, like that of an eel through the water; it will then take place under the prime conductor, at perhaps a quarter or half an inch distance, and keep a continual shaking of its tail like a fish, so that it seems animated. Turn its tail towards the prime conductor, and then it flies to your finger, and seems to nibble it. And if you hold a [pewter] plate under it at six or eight inches distance, and cease turning the globe, when the electrical atmosphere of the conductor grows small it will descend to the plate and swim back again several times with the same fish-like motion; greatly to the entertainment of spectators. By a little practice in blunting or sharpening the heads or tails of these figures, you may make them take place as desired, nearer or further from the electrified plate."

By the discharge of the battery, Franklin succeeded in melting and volatilizing gold-leaf, thin strips of tinfoil, etc. His views on the nature of light are best given in his own words.

"I am not satisfied with the doctrine that supposes particles of matter called light, continually driven off from the sun's surface, with a swiftness so prodigious! Must not the smallest particle conceivable have, with such a motion, a force exceeding that of a twenty-four pounder discharged from a cannon?... Yet these particles, with this amazing motion, will not drive before them, or remove, the least and lightest dust they meet with.

"May not all the phenomena of light be more conveniently solved by supposing universal space filled with a subtile elastic fluid, which, when at rest, is not visible, but whose vibrations affect that fine sense in the eye, as those of air do the grosser organs of the ear? We do not, in the case of sound, imagine that any sonorous particles are thrown off from a bell, for instance, and fly in straight lines to the ear; why must we believe that luminous particles leave the sun and proceed to the eye? Some diamonds, if rubbed, shine in the dark without losing any part of their matter. I can make an electrical spark as big as the flame of a candle, much brighter, and therefore visible further; yet this is without fuel; and I am persuaded no part of the electrical fluid flies off in such case to distant places, but all goes directly and is to be found in the place to which I destine it. May not different degrees of the vibration of the abovementioned universal medium occasion the appearances of different colours? I think the electric fluid is always the same; yet I find that weaker and stronger sparks differ in apparent colour, some white, blue, purple, red: the strongest, white; weak ones, red. Thus different degrees of vibration given to the air produce the seven different sounds in music, analogous to the seven colours, yet the medium, air, is the same."

Mr. Kinnersley having called Franklin's attention to the fact that a sulphur globe when rubbed produced electrification of an opposite kind from that produced by a glass globe, Franklin repeated the experiment, and noticed that the discharge from the end of a wire connected with the conductor was different in the two cases, being "long, large, and much diverging when the glass globe is used, and makes a snapping (or rattling) noise; but when the sulphur one is used it is short, small, and makes a hissing noise; and just the reverse of both happens when you hold the same wire in your hand and the globes are worked alternately.... When the brush is long, large, and much diverging, the body to which it is joined seems to be throwing the fire out; and when the contrary appears it seems to be drinking in."

On October 19, 1752, Franklin wrote to Mr. Peter Collinson as follows:—

As frequent mention is made in public papers from Europe of the success of the Philadelphia experiment for drawing the electric fire from clouds by means of pointed rods of iron erected on high buildings, etc., it may be agreeable to the curious to be informed that the same experiment has succeeded in Philadelphia, though made in a different and more easy manner, which is as follows:—

Make a small cross of two light strips of cedar, the arms so long as to reach to the four corners of a large thin silk handkerchief when extended. Tie the corners of the handkerchief to the extremities of the cross, so you have the body of a kite; which, being properly accommodated with a tail, loop, and string, will rise in the air like those made of paper; but this being of silk is fitter to bear the wet and wind of a thunder-gust without tearing. To the top of the upright stick of the cross is to be fixed a very sharp-pointed wire, rising a foot or more above the wood. To the end of the twine, next the hand, is to be tied a silk ribbon, and, where the silk and twine join, a key may be fastened. This kite is to be raised when a thunder-gust appears to be coming on, and the person who holds the string must stand within a door or window, or under some cover so that the silk ribbon may not be wet, and care must be taken that the twine does not touch the frame of the door or window. As soon as any of the thunder-clouds come over the kite, the pointed wire will draw the electric fire from them, and the kite, with all the twine, will be electrified, and the loose filaments of the twine will stand out every way, and be attracted by an approaching finger. And when the rain has wetted the kite and twine so that it can conduct the electric fire freely, you will find it stream out plentifully from the key on the approach of your knuckle. At this key the phial may be charged, and from electric fire there obtained spirits may be kindled, and all the other electric experiments be performed which are usually done by the help of a rubbed glass globe or tube, and thereby the sameness of the electric matter with that of lightning completely demonstrated.

Having, in September, 1752, erected the iron rod and bells in his own house, as previously mentioned, Franklin succeeded, in April, 1753, in charging a Leyden jar from the rod, and found its charge was negative. On June 6, however, he obtained a positive charge from a cloud. The results of his observations led him to the conclusion "That the clouds of a thunder-gust are most commonly in a negative state of electricity, but sometimes in a positive state."

In order to illustrate a theory respecting the electrification of clouds, Franklin placed a silver can on a wine-glass. Inside the can was placed a considerable length of chain, which could be drawn out by means of a silk thread. He electrified the can from a Leyden jar until it would receive no more electricity. Then raising the silk thread, he gradually drew the chain out of the can, and found that the greater the length of chain drawn out the greater was the charge which the jar would give to the system, and as the chain was raised, spark after spark passed from the jar to the silver can, thus showing that the capacity of the system was increased by increasing the amount of chain exposed.

In 1755 Franklin observed the effects of induction; for, having attached to his prime conductor a tassel made of damp threads and electrified the conductor, he found that the threads repelled each other and stood out. Bringing an excited glass tube near the other end of the conductor, the threads were found to diverge more, "because the atmosphere of the prime conductor is pressed by the atmosphere of the excited tube, and driven towards the end where the threads are, by which each thread acquires more atmosphere." When the excited tube was brought near the threads, they closed a little, "because the atmosphere of the glass tube repels their atmospheres, and drives part of them back on the prime conductor." A number of other experiments illustrating electrical induction were also carried out.

In writing to Dr. Living, of Charlestown, under date March 18, 1755, Franklin gave the following extracts of the minutes of his experiments as explaining the train of thought which led him to attempt to obtain electricity from the clouds:—

"November 7, 1749. Electrical fluid agrees with lightning in these particulars: 1. Giving light. 2. Colour of the light. 3. Crooked direction. 4. Swift motion. 5. Being conducted by metals. 6. Crack or noise in exploding. 7. Subsisting in water or ice. 8. Rending bodies it passes through. 9. Destroying animals. 10. Melting metals. 11. Firing inflammable substances. 12. Sulphureous smell. The electric fluid is attracted by points. We do not know whether this property is in lightning. But since they agree in all the particulars wherein we can already compare them, is it not probable they agree likewise in this? Let the experiment be made."

Another experiment very important in its bearing on the theory of electricity was described by Franklin in the same letter to Dr. Living. It was afterwards repeated in a much more complete form by Cavendish, who deduced from it the great law that electrical repulsion varies inversely as the square of the distance between the charges. The same experiment was repeated in other forms by Faraday, who had no means of knowing what Cavendish had done. Franklin writes:—

I electrified a silver fruit-can on an electric stand, and then lowered into it a cork ball of about an inch in diameter, hanging by a silk string, till the cork touched the bottom of the can. The cork was not attracted to the inside of the can, as it would have been to the outside, and though it touched the bottom, yet, when drawn out, it was not found to be electrified by that touch, as it would have been by touching the outside. The fact is singular. You require the reason? I do not know it. Perhaps you may discover it, and then you will be so good as to communicate it to me. I find a frank acknowledgment of one's ignorance is not only the easiest way to get rid of a difficulty, but the likeliest way to obtain information, and therefore I practise it. I think it is an honest policy.

A note appended to this letter runs as follows:—

Mr. F. has since thought that, possibly, the mutual repulsion of the inner opposite sides of the electrized can may prevent the accumulating an electric atmosphere upon them, and occasion it to stand chiefly on the outside. But recommends it to the further examination of the curious.

The explanation in this note is the correct one, and from the fact that in the case of a completely closed hollow conductor the charge is not only chiefly but wholly on the outside, the law of inverse squares above referred to follows as a mathematical consequence.

On writing to M. Dalibard, of Paris, on June 29, 1755, Franklin complained that, though he always (except once) assigned to lightning-rods the alternative duty of either preventing a stroke or of conducting the lightning with safety to the ground, yet in Europe attention was paid only to the prevention of the stroke, which was only a part of the duty assigned to the conductors. This is followed by the description of the effect of a stroke upon a church-steeple at Newbury, in New England. The spire was split all to pieces, so that nothing remained above the bell. The lightning then passed down a wire to the clock, then down the pendulum, without injury to the building. "From the end of the pendulum, down quite to the ground, the building was exceedingly rent and damaged, and some stones in the foundation-wall torn out and thrown to the distance of twenty or thirty feet." The pendulum-rod was uninjured, but the fine wire leading from the bell to the clock was vaporized except for about two inches at each end.

Mr. James Alexander, of New York, having proposed to Franklin that the velocity of the electric discharge might be measured by discharging a jar through a long circuit of river-water, Franklin, in his reply, explained that such an experiment, if successful, would not determine the actual velocity of electricity in the conductor. He compared the electricity in conductors to an incompressible fluid, so that when a little additional fluid is injected at one end of a conductor, an equal amount must be extruded at the other end—his view apparently being identical with that of Maxwell, who held that all electric displacements must take place in closed circuits.

"Suppose a tube of any length open at both ends.... If the tube be filled with water, and I inject an additional inch of water at one end, I force out an equal quantity at the other in the very same instant.

"And the water forced out at one end of the tube is not the very same water that was forced in at the other end at the same time; it was only one motion at the same time.

"The long wire, made use of in the experiment to discover the velocity of the electric fluid, is itself filled with what we call its natural quantity of that fluid, before the hook of the Leyden bottle is applied at one end of it.

"The outside of the bottle being at the time of such application in contact with the other end of the wire, the whole quantity of electric fluid contained in the wire is, probably, put in motion at once.

"For at the instant the hook, connected with the inside of the bottle, gives out, the coating or outside of the bottle draws in, a portion of that fluid....

"So that this experiment only shows the extreme facility with which the electric fluid moves in metal; it can never determine the velocity.

"And, therefore, the proposed experiment (though well imagined and very ingenious) of sending the spark round through a vast length of space, by the waters of Susquehannah, or Potowmack, and Ohio, would not afford the satisfaction desired, though we could be sure that the motion of the electric fluid would be in that tract, and not underground in the wet earth by the shortest way."

In his investigations of the source of electricity in thunder-clouds, Franklin tried an experiment which has been frequently repeated with various modifications. Having insulated a large brass plate which had been previously heated, he sprinkled water upon it, in order, if possible, to obtain electricity by the evaporation of the water, but no trace of electrification could be detected.

During his visit to England, Franklin wrote many letters to Mr. Kinnersley and others on philosophical questions, but they consisted mainly of accounts of the work done by other experimenters in England, his public business occupying too much of his attention to allow him to conduct investigations for himself. In one of his letters, speaking of Lord Charles Cavendish, he says:—

It were to be wished that this noble philosopher would communicate more of his experiments to the world, as he makes many, and with great accuracy.

When the controversy between the relative merits of points and knobs for the terminals of lightning-conductors arose, Franklin wrote to Mr. Kinnersley:—

Here are some electricians that recommend knobs instead of points on the upper end of the rods, from a supposition that the points invite the stroke. It is true that points draw electricity at greater distances in the gradual silent way; but knobs will draw at the greatest distance a stroke. There is an experiment which will settle this. Take a crooked wire of the thickness of a quill, and of such a length as that, one end of it being applied to the lower part of a charged bottle, the upper may be brought near the ball on the top of the wire that is in the bottle. Let one end of this wire be furnished with a knob, and the other may be gradually tapered to a fine point. When the point is presented to discharge the bottle, it must be brought much nearer before it will receive the stroke than the knob requires to be. Points, besides, tend to repel the fragments of an electrical cloud; knobs draw them nearer. An experiment, which I believe I have shown you, of cotton fleece hanging from an electrized body, shows this clearly when a point or a knob is presented under it.

The following quotation from Franklin's paper on the method of securing buildings and persons from the effects of lightning is worthy of attention, for of late years a good deal of money has been wasted in providing insulators for lightning-rods. A few years ago the vicar and churchwardens of a Lincolnshire parish were strongly urged to go to the expense of insulating the conductor throughout the whole height of the very lofty tower and spire of their parish church. Happily they were wise enough to send the lightning-rod man about his business. But this is not the only case which has come under the writer's notice, showing that there is still a widespread impression that lightning-conductors should be carefully insulated. Franklin says:—

"The rod may be fastened to the wall, chimney, etc., with staples of iron. The lightning will not leave the rod (a good conductor) to pass into the wall (a bad conductor) through these staples. It would rather, if any were in the wall, pass out of it into the rod, to get more readily by that conductor into the earth."[2]