Part 11 (1/2)

_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.