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Recent Advances in Telegraphy. [July, 
the corresponding note is faintly audible. To intensify the 
effeCt the line current, in practice, is simply passed to earth 
through the “ primary,” p, of an induCtion-coil, and the 
more intense secondary current is used. In the figure, b is 
a hollow wooden resonance-box, with a bulging zinc face, b. 
This box is carried by a metal axle, A, supported by a stand, 
s : it is rotated by turning the handle, E. The zinc face is 
connected by a wire, w, to the axle ; h is merely an air-hole 
in the face of the box. One end of the “ secondary coil,” 
s, is connected by wire to the metal axle at the terminal a ; 
the other end is connected to a bare wire held in the ope- 
rator’s hand, as shown. The operator lightly presses a 
finger of this hand on the zinc face, while with the other 
he rotates the box, and the dry rasp of the skin on the zinc 
surface is changed into a musical note whenever the current 
passes. 
Like M. la Cour, Gray also provides that the vibratory 
current shall close a local circuit and record the message in 
permanent marks, by means of a Morse or other recording 
instrument. For this purpose he employs a receiver similar 
to the string-transmitter shown in Fig. 14. The line cur- 
rent, passing through the magnets of this instrument, sets 
the tense bar in vibration against the upper contact c, thus 
closing the local circuit and actuating the local recorder. 
Mr. Gray’s apparatus is now successfully operated over 
more than 2400 miles of the Western Union Telegraph 
Company’s lines, including distances of several hundred 
miles. As many as four, and even eight, messages are 
simultaneously sent. Both he and M. la Cour are still 
engaged in perfecting their apparatus, and we may reason- 
ably expeCt that the telephone will ere long do good service 
as a practical telegraph. 
b. The Articulating Telephone . 
This ingenious little instrument is the most wonderful of 
all the forms of telephone, and the latest, as it is the 
greatest, to use the words of Sir Wiiliam Thomson, “ of all 
the marvels of the eleCtric telegraph.” Its peculiar faculty 
lies in the transmission of promiscuous sounds. Not only 
does it convey the blended notes of musical instruments, 
but it actually reproduces the human speech. It is easy to 
see how an instrument like this will become practically 
useful. For domestic or commercial purposes, for reports 
of lectures and speeches it is especially fit. It has the 
advantage of quickness over ordinary methods of telegraphing. 
