_Dr. Darwin to Mr. Edgeworth._

DERBY, March 15, 1795.

DEAR SIR,--I beg your pardon for not immediately answering your last favor, which was owing to the great influence the evil demon has at present in all affairs on this earth. That is, I lost your letter, and have in vain looked over some scores of papers, and cannot find it.

Secondly, having lost your letter, I daily hoped to find it again--without success.

The telegraph you described I dare say would answer the purpose. It would be like a giant wielding his long arms and talking with his fingers; and those long arms might be covered with lamps in the night.

You would place four or six such gigantic figures in a line, so that they should spell a whole word at once; and other such figures in sight of each other, all round the coast of Ireland; and thus fortify yourselves, instead of Friar Bacon's wall of bra.s.s round England, with the brazen head, which spoke, "Time is! Time was! Time is past!"

MR. EDGEWORTH'S MACHINE.

Having slightly mentioned the contrivances made use of by the ancients for conveying intelligence swiftly, and having pointed out some of the various important uses to which this art may be applied, I shall endeavor to give a clear view of my attempts on this subject.

Models of the French telegraph have been so often exhibited, and the machine itself is so well known, that it is not necessary to describe it minutely in this place. It is sufficient to say that it consists of a tall pole, with three movable arms, which may be seen at a considerable distance through telescopes; these arms may be set in as many different positions as are requisite to express all the different letters of the alphabet. By a successive combination of letters shown in this manner, words and sentences are formed and intelligence communicated. No doubt can be made of the utility of this machine, as it has been applied to the most important purposes. It is obviously liable to mistakes, from the number of changes requisite for each word, and from the velocity with which it must be moved to convey intelligence with any tolerable expedition.

The name, however, which is well chosen, has become so familiar, that I shall, with a slight alteration, adopt it for the apparatus which I am going to describe. _Telegraph_ is a proper name for a machine which describes at a distance. _Telelograph_, or contractedly _Tellograph_, is a proper name for a machine that describes _words_ at a distance.

Dr. Hooke, to whom every mechanic philosopher must recur, has written an essay upon the subject of conveying swift intelligence, in which he proposes to use large wooden letters in succession. The siege of Vienna turned his attention to the business. His method is more c.u.mbrous than the French telegraph, but far less liable to error.

I tried it before I had seen Hooke's work, in the year 1767 in London, and I could distinctly read letters illuminated with lamps in Hampstead Churchyard, from the house of Mr. Elers in Great Russell Street, Bloomsbury, to whom I refer for date and circ.u.mstance. To him and to Mr.

E. Delaval, F.R.S., to Mr. Perrot, of Hare Hatch, and to Mr Woulfe the chemist, I refer for the precedency which I claim in this invention. In that year I invented the idea of my present tellograph, proposing to make use of windmill sails instead of the hands or pointers which I now employ. Mr. Perrot was so good as to accompany me more than once to a hill near his house to observe with a telescope the windmill at Nettlebed, which places are, I think, sixteen miles asunder. My intention at that time was to convey not only a swift but an unsuspected mode of intelligence. By means of common windmills this might have been effected, before an account of the French telegraph was made public.

My machinery consists of four triangular pointers or hands [each upon a separate pedestal, ranged along in a row], each of which points like the hand of a clock to different situations in the circles which they describe. It is easy to distinguish whether a hand moving vertically points perpendicularly downwards or upwards, horizontally to the right or left, or to any of the four intermediate positions.

The eye can readily perceive the eight different positions in which one of the pointers is represented [on the plate attached to the article in the "Transactions," but here omitted]. Of these eight positions seven only are employed to denote figures, the upright position of the hand or pointer being reserved to represent o, or zero. The figures thus denoted refer to a vocabulary in which all the words are numbered. Of the four pointers, that which appears to the left hand of the observer represents thousands; the others hundreds, tens, and units, in succession, as in common numeration.

[By these means, as Mr. Edgeworth showed, numbers from 1 up to 7,777, omitting those having a digit above 7, could be displayed to the distant observer, who on referring to his vocabulary discovered that they meant such expressions as it might seem convenient to transmit by this excellent invention.]

Although the electric telegraphs have long since superseded telegraphs of this cla.s.s in public use, the young people of Colonel Ingham's cla.s.s took great pleasure in the next summer in using Mr. Edgeworth's telegraph to communicate with each other, by plans easily made in their different country homes.

It may interest the casual reader to know that the first words in the first message transmitted on the telegraph between Scotland and Ireland, alluded to above, were represented by the numbers 2,645, 2,331, 573, 1,113 244, 2,411, 6,336, which being interpreted are,--

"Hark from basaltic rocks and giant walls,"

and so on with the other lines, seven in number. This is Mr. Edgeworth's concise history of telegraphy before his time.

The art of conveying intelligence by sounds and signals is of the highest antiquity. It was practised by Theseus in the Argonautic expedition, by Agamemnon at the siege of Troy, and by Mardonius in the time of Xerxes. It is mentioned frequently in Thucydides. It was used by Tamerlane, who had probably never heard of the black sails of Theseus; by the Moors in Spain; by the Welsh in Britain; by the Irish; and by the Chinese on that famous wall by which they separated themselves from Tartary.

All this detail about Mr. Edgeworth's telegraph resulted in much search in the older encyclopaedias. Quite full accounts were found, by the young people, of his system, and of the French system afterwards employed, and worked in France until the electric telegraph made all such inventions unnecessary.

Before the next meeting, Bedford Long, who lived on Highland Street in Roxbury, and Hugh, who lived on the side of Corey Hill, were able to communicate with each other by semaph.o.r.e; and at the next meeting they arranged two farther stations, so that John, at Cambridge, and Jane Fortescue, at Lexington, were in the series.

There being some half an hour left that afternoon, the children amused themselves by looking up some other of Mr. Edgeworth's curious experiments and vagaries.

MORE OF MR. EDGEWORTH'S FANCIES.

During my residence at Hare Hatch another wager was proposed by me among our acquaintance, the purport of which was that I undertook to find a man who should, with the a.s.sistance of machinery, walk faster than any other person that could be produced. The machinery which I intended to employ was a huge hollow wheel, made very light, withinside of which, in a barrel of six feet diameter, a man should walk. Whilst he stepped thirty inches, the circ.u.mference of the large wheel, or rather wheels, would revolve five feet on the ground; and as the machinery was to roll on planks and on a plane somewhat inclined, when once the _vis inertiae_ of the machine should be overcome, it would carry on the man within it as fast as he could possibly walk. I had provided means of regulating the motion, so that the wheel should not run away with its master. I had the wheel made; and when it was so nearly completed as to require but a few hours' work to finish it, I went to London for Lord Effingham, to whom I had promised that he should be present at the first experiment made with it. But the bulk and extraordinary appearance of my machine had attracted the notice of the country neighborhood; and, taking advantage of my absence, some idle curious persons went to the carpenter I employed, who lived on Hare Hatch Common. From him they obtained the great wheel which had been left by me in his care. It was not finished.

I had not yet furnished it with the means of stopping or moderating its motion. A young lad got into it; his companions launched it on a path which led gently down hill towards a very steep chalk-pit. This pit was at such a distance as to be out of their thoughts when they set the wheel in motion. On it ran. The lad withinside plied his legs with all his might. The spectators, who at first stood still to behold the operation, were soon alarmed by the shouts of their companion, who perceived his danger. The vehicle became quite ungovernable; the velocity increased as it ran down hill. Fortunately the boy contrived to jump from his rolling prison before it reached the chalk-pit; but the wheel went on with such velocity as to outstrip its pursuers, and, rolling over the edge of the precipice, it was dashed to pieces.

The next day, when I came to look for my machine, intending to try it on some planks which had been laid for it, I found, to my no small disappointment, that the object of all my labors and my hopes was lying at the bottom of a chalk-pit, broken into a thousand pieces. I could not at that time afford to construct another wheel of this sort, and I cannot therefore determine what might have been the success of my scheme.

As I am on the subject of carriages, I shall mention a sailing-carriage that I tried on this common. The carriage was light, steady, and ran with amazing velocity. One day, when I was preparing for a sail in it with my friend and schoolfellow Mr. William Foster, my wheel-boat escaped from its moorings just as we were going to step on board. With the utmost difficulty I overtook it; and as I saw three or four stage-coaches on the road, and feared that this sailing-chariot might frighten their horses, I, at the hazard of my life, got into my carriage while it was under full sail, and then, at a favorable part of the road, I used the means I had of guiding it easily out of the way. But the sense of the mischief which must have ensued if I had not succeeded in getting into the machine at the proper place and stopping it at the right moment was so strong as to deter me from trying any more experiments on this carriage in such a dangerous place.

Such should never be attempted except on a large common, _at a distance from a high_ road. It may not, however, be amiss to suggest that upon a long extent of iron railway in an open country carriages properly constructed might make profitable voyages, from time to time, with sails instead of horses; for though a constant or regular intercourse could not be thus carried on, yet goods of a certain sort, that are salable at any time, might be stored till wind and weather were favorable.

When Bedford had read this pa.s.sage, John Fordyce said he had travelled hundreds of miles on the Western railways where Mr. Edgeworth's sails could have been applied without a "stage-coach" to be afraid of them.

JACK THE DARTER.

In one of my journeys from Hare Hatch to Birmingham, I accidentally met with a person whom I, as a mechanic, had a curiosity to see. This was a sailor, who had amused London with a singular exhibition of dexterity.

He was called _Jack the Darter_. He threw his darts, which consisted of thin rods of deal of about half an inch in diameter and of a yard long, to an amazing height and distance; for instance, he threw them over what was then called the New Church in the Strand. Of this feat I had heard, but I entertained some doubts upon the subject. I had inquired from my friends where this man could be found, but had not been able to discover him. As I was driving towards Birmingham in an open carriage of a singular construction, I overtook a man who walked remarkably fast, but who stopped as I pa.s.sed him, and eyed my equipage with uncommon curiosity. There was something in his manner that made me speak to him; and from the sort of questions he asked about my carriage, I found that he was a clever fellow. I soon learned that he had walked over the greatest part of England, and that he was perfectly acquainted with London. It came into my head to inquire whether he had ever seen the exhibition about which I was so desirous to be informed.

"Lord! sir," said he, "I am myself Jack the Darter." He had a roll of brown paper in his hand, which he unfolded, and soon produced a bundle of the light deal sticks which he had the power of darting to such a distance. He readily consented to gratify my curiosity; and after he had thrown some of them to a prodigious height, I asked him to throw some of them horizontally. At the first trial he threw one of them eighty yards with great ease. I observed that he coiled a small string round the stick, by which he gave it a rotary motion that preserved it from altering its course; and at the same time it allowed the arm which threw it time to exercise its whole force.

If anything be simply thrown from the hand, it is clear that it can acquire no greater velocity than that of the hand that throws it; but if the body that is thrown pa.s.ses through a greater s.p.a.ce than the hand, whilst the hand continues to communicate motion to the body to be impelled, the body will acquire a velocity nearly double to that of the hand which throws it. The ancients were aware of this; and they wrapped a thong of leather round their javelins, by which they could throw them with additional violence. This invention did not, I believe, belong to the Greeks; nor do I remember its being mentioned by Homer or Xenophon.

It was in use among the Romans, but at what time it was introduced or laid aside I know not. Whoever is acquainted with the science of projectiles will perceive that this invention is well worthy of their attention.

A ONE-WHEELED CHAISE.

After having satisfied my curiosity about Jack the Darter, I proceeded to Birmingham. I mentioned that I travelled in a carriage of a singular construction. It was a one-wheeled chaise, which I had had made for the purpose of going conveniently in narrow roads. It was made fast by shafts to the horse's sides, and was furnished with two weights or counterpoises, that hung below the shafts. The seat was not more than eight and twenty or thirty inches from the ground, in order to bring the centre of gravity of the whole as low as possible. The footboard turned upon hinges fastened to the shafts, so that when it met with any obstacle it gave way, and my legs were warned to lift themselves up. In going through water my legs were secured by leathers, which folded up like the sides of bellows; by this means I was pretty safe from wet. On my road to Birmingham I pa.s.sed through Long Compton, in Warwickshire, on a Sunday. The people were returning from church, and numbers stopped to gaze at me. There is, or was, a shallow ford near the town, over which there was a very narrow bridge for horse and foot pa.s.sengers, but not sufficiently wide for wagons or chaises. Towards this bridge I drove.

The people, not perceiving the structure of my one-wheeled vehicle, called to me with great eagerness to warn me that the bridge was too narrow for carriages. I had an excellent horse, which went so fast as to give but little time for examination. The louder they called, the faster I drove; and when I had pa.s.sed the bridge, they shouted after me with surprise. I got on to Shipstone upon Stone; but before I had dined there I found that my fame had overtaken me. My carriage was put into a coach-house, so that those who came from Long Compton, not seeing it, did not recognize me. I therefore had an opportunity of hearing all the exaggerations and strange conjectures which were made by those who related my pa.s.sage over the narrow bridge. There were posts on the bridge, to prevent, as I suppose, more than one horseman from pa.s.sing at once. Some of the spectators a.s.serted that my carriage had gone over these posts; others said that it had not wheels, which was indeed literally true; but they meant to say that it was without any wheel.

Some were sure that no carriage ever went so fast; and all agreed that at the end of the bridge, where the floods had laid the road for some way under water, my carriage swam on the surface of the water.

VIII.

JAMES WATT.

"Uncle Fritz," said Mabel Liddell, the next afternoon that our friends had gathered together for a reading, "would it not be well for us all to go down into the kitchen this afternoon, and watch the steam come out of the kettle as Ellen makes tea for us?"

"Why should it be well, Mabel?" said Colonel Ingham. "For my part, I should prefer to remain in my own room, more especially as I consider my armchair to be more suited to the comfort of one already on the downward path in life than is the kitchen table, where we should have to sit should we invade the premises of our friends below."

"I was thinking," said Mabel, "of the manner in which James Watt when a child invented the steam-engine, from observing the motion of the top of the teakettle; and as we are to read about Watt this afternoon I thought we might be in a more fit condition to understand his invention, and might more fully comprehend his frame of mind while perfecting his great work, should we also fix our eyes and minds on the top of the teakettle in Ellen's kitchen."

"Mabel, my child," said Uncle Fritz, "you talk like a book, and a very interesting one at that; but I think, as the youngest of us would say, that you are just a little off in your remarks. And as I observe that Clem, who is going to read this afternoon, desires to deliver a sermon of which your conversation seems to be the text, I will request all to listen to him before we consider seriously vacating this apartment, however poor it may be,"--and he glanced fondly around at the comfortable arrangements that everywhere pervaded the study,--"and seek the regions below."

"I only wanted to say," began Clem, "that although Watt did on one occasion (in his extreme youth) look at a teakettle with some interest, he was not in the habit, at the time when he devoted most thought to the steam-engine, of having a teakettle continually before him that he might gain inspiration from observing the steam issue from its nose. And, as Watt dispensed with this aid, I have no doubt that we may do so as well, contenting ourselves with the results of the experiments in the vaporization of water, which Ellen is now conducting in the form of tea.

Besides all this, however, I do want to say some things, before we read aloud this afternoon (I hope this isn't really too much like a sermon), about the steam-engine and the part that Watt had in perfecting it."