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 cumbrous 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 circumstance. 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 class in public use, the young people of Colonel Ingham's class 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.