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POPULAR SCIENCE REVIEW. 
the nodal points in a bugle of hyperbolic figure, giving the correct intervals, 
were then shown experimentally and explained ; the difference in position 
between these and the nodes of similar notes on a cone being very great. 
The bugle used had for the pitch of its prime or fundamental note 0 of 
128 vib., and was divided into seven semi-ventral segments for C of 512 vib. 
This 0 could be produced from each of these seven pieces, or from any 
combination of an odd number of adjacent pieces, and the effect of the 
gradual increase of curvature from the mouthpiece to the bell upon the 
positions of the nodal points, and consequently upon the lengths of the semi- 
ventral segments, was thus made apparent. 
Telephonic Signals . — The telephone, wonderful instrument as it is, is still 
far from realizing the ideas entertained of it by the general public, who are 
generally inclined to fancy that the extraordinary results foreshadowed by 
the facetious Mr. Punch have already been attained. It is still impossible 
for a serious family to remain quietly in their own drawing-room on a wet 
Sunday and satisfy their consciences by listening there to the suave eloquence 
of some popular preacher ; for ladies of musical tastes to enliven their 
soirees with melodies “ wired ” from Covent Garden or the Haymarket ; or 
for scientific amateurs to enjoy the discourses delivered for their delectation 
at the Roj r al Institution without the labour of travelling to Albemarle 
Street. Telephonic utterances sound as if they came “ from the back 
o’ beyont,” to use an old Scotch phrase ; and even these faint adumbrations 
of speech can only be perceived when the receiving instrument is held 
close to the ear of the listener. Hence arises a difficulty, namely, how 
is the intended recipient of a message to be warned that a communication 
is about to be made ? for it is obviously too much to expect that the 
persons at the two ends of a telephonic line shall sit perpetually with 
the instruments applied to their ears. Mr. W. C. Rontgen indicates 
(“ Nature,” December 27, 1877) that a warning may be given by means 
of a battery and alarum attached to the telephonic system, but that this 
will cause so great an addition to the cost of establishing and main- 
taining a telephonic apparatus that it must be dismissed as inadmissible. 
His own plan is to give a signal of the intended transmission of a message 
by means of a tuning-fork placed close to the end of the bar magnet, opposite 
to that which acts in reproducing the vocal sounds. He proposes to effect 
this by providing the second pole with a coil of wire inserted in the circuit 
at this point, and connected with the general circuit in a manner easily under- 
stood but hardly explicable without a figure. u Before this pole of the 
magnet,” he says, “ may be very easily set up a tuning-fork, which, with the 
telephone, is simply fixed to a resonance case ; this arrangement should be 
made at both the transmitting and receiving stations, and both forks should 
be in unison. If now the sending station wish to signal that a communication 
is to be begun, the fork of that place will be sounded with a fiddle-bow ; 
the currents thereby induced in the coil are powerful enough to set the fork 
of the receiving station in such intense vibration that the sound may be dis- 
tinctly heard in a large room.” Mr. Rontgen says that he has made this 
experiment in a room containing about 100 people, all of whom could hear 
the sounds of the fork, which was a Konig Ut 4 . The author has made 
some experiments which are of interest. One is of importance in connection 
