[19] [That is, at any single demagnetisation of the needle, it vibrates and emits the same tone as if it had been struck or mechanically caused to vibrate longitudinally.]—S. P. T.
[20] [This range was simply due to the degree of tension of the tympanum; another tympanum differently stretched, or of different proportions, would have a different range according to circumstances.]—S. P. T.
[21] [The so-called “galvanic tone” heard on opening or closing the circuit was well-known, and Wertheim had shown that this tone was, for any given rod of iron, identical with its “longitudinal tone,” i.e. the tone produced by striking it on the end so as to produce longitudinal vibrations. But it was one of the most important discoveries in Reis’s researches that such a rod could take up any tone in obedience to the vibrations forced upon it by periodic interruptions in the magnetising current in the spiral of any degree of rapidity within very wide limits. The translator has had occasion to examine this point, and has found iron, steel, and cobalt wires varying from 4 to 10 inches in length, including some used by Reis himself as receivers, to be capable of taking up vibrations from as slow as 40 per second to the very shrillest whistle audible to human ears, or exceeding 36,000 per second. It is sometimes also mistakenly supposed that such a wire can respond only to the vibrations of tones that are musical, not to those that are articulate, including both consonants and vowels. This, however, is an entire mistake. For, using such a wire as a receiver (surrounded by its proper coil and mounted with an appropriate sounding board, or, better still, tympanum), in conjunction with a well-adjusted transmitter, the articulation transmitted surpasses that obtainable with any of the ordinary magnetic receivers in distinctness, though not in loudness. This discovery of Reis’s is of the greatest importance, especially as some who ought to know better have very unjustly denied the capability of this part of the apparatus to act as a telephone receiver for articulate sounds.]—S. P. T.
[22] [This limit is a mistake of Professor Böttger’s. The longitudinal tone of an unstrained iron or steel wire 10 inches long would be a note about four octaves above the middle c of the piano; whereas, in fact, any note of the whole piano-gamut down to the lowest note, can be reproduced by such a wire, as stated in preceding footnote.]—S. P. T.
[23] [Professor Böttger had not to wait long for the fulfilment to a very large degree of this anticipation; for within six months Dingler’s Journal, in which this article appeared, contained Legat’s report on Reis’s instruments, in which not only were various modifications in their construction made known, but also the transmission of voice-tones, not yet perfectly but with recognisable modulations and intonations, was recorded. Reis had, indeed, succeeded nearly as well as this with his first instrument, as his memoir of 1861 shows. See p. 58.]
[24] [Compare ‘Die Geschichte und Entwickelung des Fernsprechwesens,’ a pamphlet issued officially in 1880 from the Imperial German Post-Office in Berlin, p. 6.]
[25] [Plate VIII. of the original in Vol. IX. of the Zeitschrift.]
[26] [Plate IX. of the original Memoir.]
[27] [This word, as the context and ending of the paragraph shows, should have been spelled tones. The letter, written in English by Reis himself, is wonderfully free from inaccuracies of composition; the slip here noted being a most pardonable one since the plural of the German “ton” is “tönen,” the very pronunciation of which would account for the confusion in the mind of one unaccustomed to write in English. So far as is known, this is the only piece of English composition ever attempted by Reis.—S. P. T.]
[28] [Reis here sketched a figure identical in all its parts with that which a fortnight later was issued in his ‘Prospectus.’ His sketch is reproduced in facsimile in Fig. 28.]