Extract from recent letter from Mr. J. J. Fahie to Prof. Hughes.
“Dear Prof. Hughes: I have now in the press a history of Wireless Telegraphy from 1838 to 1899, and in writing to Sir William Crookes for information he tells me that many years ago he saw some experiments of yours with the microphone, in which you signalled from one part of a house to another without connecting wires, and he desires me to refer to you for particulars. I think, with Sir William, that it is a pity you have not hitherto published your results, and I sincerely hope you will now do so. If also you would kindly favour me with a short account, I could find room for it in my book, which is now in the printer’s hands.—Sincerely yours,
J. J. Fahie.
Claremont Hill, St. Helier’s, Jersey,
April 26, 1899.”
Reply from Prof. D. E. Hughes:—
40, Langham-street, W.,
April 29, 1899.
Dear Sir: In reply to yours of the 26th inst., in which you say that Sir William Crookes has told you “that he saw some experiments of mine on aërial telegraphy, in about December, 1879, of which he thinks I ought to have published an account,” and of which you ask for some information, I beg to reply with a few leading experiments that I made on this subject from 1879 up to 1886:—
“In 1879, being engaged upon experiments with my microphone, together with my induction balance, I remarked that at some time I could not get a perfect balance in the induction balance, through apparent want of insulation in the coils, but investigation showed me that the real cause was some loose contact or microphonic joint excited in some portion of the circuit. I then applied the microphone in the circuit, and found that it gave a current or sound in the telephone receiver, no matter if the microphone was placed direct in the circuit, or placed independently at several feet distance from the coils, through which an intermittent current was passing. After numerous experiments, I found that the effect was entirely caused by the extra current produced in the primary coil of the induction balance.
“Further researches proved that an interrupted current, in any coil, through which an electric current was sent, gave out at each interruption of the primary current, such intense extra currents, that the whole atmosphere in the room (or in several rooms distant) would have a momentary invisible charge, which became evident if a microphonic joint was used as a receiver to a telephone. This led me to experiment upon the best form of a receiver for these invisible electric waves, which evidently permeated great distances, and through all apparent obstacles, such as walls, &c. I found that all microphonic contacts or joints were extremely sensitive. Those formed of a hard carbon such as coke, or a combination of a piece of coke resting upon a bright steel contact, were very sensitive and self-restoring; whilst a loose contact between metals was equally sensitive, but would cohere, or remain in full contact, after the passage of an electric wave.
“The sensitiveness of these microphonic contacts in metals has since been rediscovered by Mons. Ed. Branly, of Paris, and by Prof. Oliver Lodge, in England, by whom the name of ‘coherer’ has been given to this organ of reception; but, as we wish this organ to make a momentary contact and not cohere permanently, the name seems to me ill-suited for the instrument. The most sensitive and perfect receiver that I have yet made does not cohere permanently, but recovers its original state instantly, and, therefore, requires no tapping or mechanical aid to the separation of the contacts after momentarily being brought into close union.