telephone for an hour at a time, the distance of the stations from each other being about one hundred and fifty feet. He says: "I remember especially that Mr. Reis speaking through his instrument I distinctly heard the words, 'Guten Morgen, Herr Fischer'; 'Ich komme gleich'; 'Passe auf'; 'Wie viel Uhr ist es?' 'Wie heisst du?'" Heinrich Hold, a colleague of Reis in the same institute, gives detailed testimony of talking successfully through the telephone. Heinrich F. Peter, the musical teacher, then and still at Garnier's Institute, says, "Philipp Schmidt read long sentences from Spiess's 'Turnbuch,' which sentences Philipp Reis, who was listening, understood perfectly, and repeated to us." Being incredulous, and to further test it, Herr Peter spoke some impromptu nonsensical sentences through the telephone, such as "Die Sonne ist von Kupfer," which Reis understood as "Die Sonne ist von Zucker."
Mr. S. M. Yeates, instrument-maker of Dublin, writes that in 1865 he exhibited Reis's telephone to the Dublin Philosophical Society, substituting an improved electro-magnetic receiver for the knitting-needle receiver (shown in Fig. 2), the transmitter being the same as in that figure. Yeates's receiver was an electro-magnet with a vibrating armature, mounted on a spring attached to a sounding-box. William Frazer, M. D., member of the Council of the Royal Irish Academy, writes, March 13, 1883, that he was present on this occasion, that various questions were asked and answered, and that "the separate words were most distinct, the singing less so." The individual who spoke was easily recognized by his voice. (It has been stated elsewhere that Yeates improved the Reis transmitter by placing a drop of water between the platinum surfaces of loose contact.)
In an appendix, which is not really separable from nor less important than the rest of the work, Professor Thompson discusses the relation of Reis's instruments to those now in use, and also Reis's development and use of the variable or "undulatory" electric current, corresponding to the undulatory curves of sound-pressure, which he graphically represents, and to which he often refers.
In the first section, Professor Thompson points out that Reis's transmitters preserve throughout, first, the tympanum to collect the voice-waves, and, second, two or more electric elements in loose or imperfect contact with each other, so combined with the tympanum that the motions of the latter correspondingly alter the current of electricity flowing between the contact-pieces. Reis's apparatus is not, therefore, an "interruptor," but a "current-regulator." The contact-pieces, one or both, were mounted with adjustable springs, or held together by gravity, so as to vary the current without completely breaking contact, in the same way, and for the same purpose, as in the Berliner, Blake, and other modern transmitters. Disregarding induction-coils and other accessories, the fundamental principle of these later instruments is the combination of a tympanum with a cur-
