a ee ee 
Se ee 
ae we 
O. N. Rood—Telephonic Relay. 59 
are too minute to be recorded by this method. It is to be 
noted, however, that the width of the line traced where the 
vibrations are extremely small, is so great as to mask the curv- 
ature, so that the experiment just cited is not entirely fair. 
The clearness and beauty of the curves obtained can hardly 
be 2 ape without inspection of the originals. Their 
complexity and variety open a large field for investigation, and 
they seem to offer the means of analysis of articulate speech. 
Art. VITI.— Suggestions for a Telephonic Relay; by Professor 
O. N. Roop. 
AFTER reading an account of the experiments of Mr. 
Hughes,* which may be regarded as an extension of the work 
of Edison, it occurred to me that the peculiar property of car- 
bon, upon which they depend, might be utilized in the con- 
struction of a telephonic relay. I accordingly arranged three 
pieces of carbon in the form of an H, attaching the two outside 
saben to the diaphragm of an ordinary telephone; this, with a 
attery, was destined to act as relay and re-transmitter. The 
first circuit included, then, a common telephone as sender, and 
the coil of the relay; the second included battery, vibrating 
carbon, and a common telephone used as a receiver. It was 
found that the vibrations of the pivots of the central piece of 
carbon were indeed able to modulate an electric current, so 
as to reproduce with somewhat diminished intensity sounds 
uttered in the sending telephone. Eight small vibrating car- 
bons were now substituted for the single piece, and the repro- 
duction was effected without loss of intensity or distinctness. 
The battery used with the relay consisted of eight small cells 
of zine aad ‘caition placed in diluted sulphuric acid only. For 
a relay to be efficient it is of course necessary that it should 
increase the loudness of the sounds so as to allow for electrical 
re-transmission to a more distant station ; this can probably be 
effected, 1st, by making the telephonic relay of such dimen- | 
sions that six or eight carbons can be placed pg etary: J 
over the center of the iron diaphragm, and 2d, by using simul. 
taneously several of these pieces of apparatus in the same 
circuit. 
An arrangement like Hughes's microphone was also employed 
instrument; an inverted cov xX was 
single one. The sd acoagrae of the carbons was due to a 
Suggestion of Dr. W. Gibbs, who at the time proposed various 
* Nature, May 16, 1878. : 
