108 REPORT—1863. 
Such character must be in its pitch and in its peculiar quality of tone (tim- 
bre), both of which should differ as much as possible from those which con- 
tend with it. The effect of interrupted sounds should also be tested. 
«‘ This is the most important portion of the inquiry. 
«©, All this is of still more moment when the air is made a discontinuous 
medium by the presence of fog, rain, or snow; and it is probable that the 
origin and quality of the sound may in such cases exert a still greater in- 
fluence than in clear weather. The remarkable power of fog to deaden the 
report of guns has often been noticed, but it should be carefully studied for 
each of the three classes of signals which have been mentioned. It is also 
possible that the signals which are best in clear weather may not be so under 
these conditions. 
«TD. Experiments are required on the degree of accuracy with which the 
direction of a sound can be ascertained; and whether such estimation can be 
assisted by a hearing-trumpet, a tense membrane, or other acoustic aids. 
«“E. It is of even greater importance to try the transmission of sound 
through water, which seems to offer peculiar advantages, if we may judge from 
the few experiments which have been made by Colladon and others, some of 
the details of which are given in a report furnished by one of us to the Bri- 
tish Association (a copy of which is transmitted with this). It may be ex- 
pected that greater distances will be commanded, that there will be fewer dis- 
turbing causes, and that the direction will be more easily determined. Such 
conclusions, at least, follow from two facts observed by Colladon. A small 
bell struck by a hammer under water was heard easily across the Lake of Ge- 
neva, at nine miles’ distance ; and its sound diverged much less behind a screen 
than it would have done in air. These subaqueous sounds, however, do not 
easily pass out from water into air, being reflected at the surface of junction ; 
and they must be listened to with a kind of hearing-tube dipped in the water. 
This presents little difficulty, and (at least in iron ships) the hull of the vessel 
may perhaps itself serve as the sound-catcher. A bell, however, is not the 
only nor even the best means of making these sounds. Small cartridges of 
powder fired under water at regular intervals would correspond to guns, and 
would undoubtedly be heard at very great distances. The Siren is still more 
promising: it isa box whose lid is made to revolve by the passage of a stream 
of some fluid through a number of oblique apertures, which are thus alter- 
nately opened and closed. This instrument gives under water a musical 
tone of extraordinary fulness and power, which could not be easily mistaken 
for any other sound. And, lastly, one of us (Professor Wheatstone) has found 
that tubes fitted with the embouchures of organ-pipes, and made to speak 
under water by a current of that fluid, produce a sound of exceeding inten- 
sity. The success of any of these subaqueous signals depends on the power 
of distinguishing them from sounds due to the vessel itself. In particular, 
the paddles or screw, and the impact of waves on the bow, must be powerful 
generators of submarine sounds; but it is highly probable that the character 
of the signal-sounds will be entirely different from them. 
“< Tf, as we hope, you feel sufficient interest in the matters above mentioned 
to direct such an investigation of them as may lead to practical results, we 
would further take the liberty of suggesting what seems to us likely to be 
the most effective and economical way of carrying it out, at the same time 
offering whatever further information we may be able to afford. 
“The experiments might centre in the flag-ship at Spithead. One of its 
officers might probably be found who would take an interest in the research, 
or a supernumerary might be appointed for this special object. He should 
