A TELEGRAPHIC EXPERIMENT.

New Zealand Times, Volume XXX, Issue 4510, 3 September 1875, Page 3

A TELEGRAPHIC EXPERIMENT.

We are accustomed to talk familiarly of the wonders of telegraphy, but it is not till we are brought face to face with what can be done by the aid of tho telegraph that we realise them. An experiment, which is probably unique in the history of telegraphy, was conducted on Saturday evening by Mr. John A. Lund (of Messrs. Barraucl and Lunds, Cornhill), at the offices of the Indo-European Telegraph Company. It was desired by Captain Sartorius, brother to the captain, of Ashanteo celebrity, who is at Teheran, Persia, to check with absolute correctness, the variation between one of the chronometers of this firm which he had there and the Greenwich time here. The instrument is not a full-chronometer, but a half-chronometer, double roller lever, pocket watch, of a kind which Messrs. Barraud and Lunds find able to stand the wear and tear of riding and pocket use, and yet keep a rate for scientific observations. To do this it was necessary to have the line clear from London to Teheran, a distance of 3700 miles. Major Smith, the telegraph superintendent, was with Captain Sartorius at the Teheran instrument, and Mr. Black was in charge of the London instrument; while Mr. Lund was in attendance with a ship’s chronometer, set to exact Greenwich time. The time here was eight o’clock, equal to about half-past 11 p.m. in Persia. The first message transmitted broke at Berlin, where the wires had not been coupled ; but shortly afterwards the message was sent through from Teheran, and was uncoiling itself on the long tape, like a piece of paper, at the Moorgate-street instrument : “ Give the signal current at nineteen past eight, and keep it on till twenty.” This was effected by holding down the small handle which connects the zinc and copper wires, thereby causing a current for the space of the minute indicated Mr. Lund calling out “ fifty-eight,” “fifty-nine,” “sixty,” as the seconds went by which completed the minute. At the word “sixty,” the handle was loosed, and Captain Sartorms would the same instant know that it was 8.20 p.m., Greenwich time. To check the minute differences of individual observations, the experiment was repeated two or three times, the result being that Captain Sartorius’s watch was shown to be about two seconds behind Greenwich time. It was necessary to take several observations, as there was something wrong with the German “relays” a time or two. The relay is a connexion with fresh batteries, which feed the wire at intervals, because if the wire were charged with a current sufficiently strong to go the whole distance itself it would soon be worn out. On the other hand, a single weak current would diffuse itself before reaching the end of so long a journey. While the current was flowing, its duration was marked by a long black line on the paper at Teheran, and when it stopped there would be a sharp “ click,” ns the pressure on the London handle was removed. Perhaps the most marvellous fact about the whole thing is that (as is well known to telegraphists) the “ earth current ” or stream of electricity which completes the circuit from battery to battery, finds its way through the earth from Teheran to Loudon without any wire or other connection whatever till it finds the battery from which it started, and this, too, instantaneously. When the experiment itself was concluded, there were a few friendly inquiries by Mr. Lund about the chronometer which Captain Sartorius took with him. How was it going 1 “ Oh, very well, thank you ; it was a second slow at Constantinople,” comes back the answer, as if only across a shop counter. “ Glad to hear it.” “Much obliged for the trouble you’ve taken in London.” “ \ ery welcome.” “ Good night.” Such exactitude of time is, of course, only absolutely necessary in scientific investigations, but in these, as in the late transit of Venus, it is of great importance to know what the true time is. Messrs. Barraud and Lunds appear to pay special attention to this one department, as their Comhill establishment is fitted in every room with the most ingenious contrivances for registering Greenwich time. In one of them, which is especially worth notice, an electric shock leaves a mark from a hand charged with ink on the face of a chronograph, thus getting rid of even the infinitessimal error arising from observation by the eye or ear in the ordinary methods.