SCIENTIFIC SUMMABY. 
211 
After briefly naming Trevelyan’s Rockers, Sondbauss’s experiment was 
shown, in which, when a bulb about three-quarters of an inch in diameter 
is blown at the end of a narrow tube 5 or 6 inches long, a sound is heard 
proceeding from the heated glass. The original observer showed that the 
vibration of the glass itself is no essential part of the action. 
If a closed tube, hot at the closed and cool at the open end, be con- 
sidered ; if the adjustment of temperature were instantaneous, heat would 
have no effect in producing vibration. But as it takes time, it follows that 
■at the phase of greatest condensation heat is received by the air, and at the 
phase of greatest rarefaction is given up from it, so that there is a tendency to 
maintain the vibrations. A great range of temperature is necessary for the 
maintenance of vibration, and the transfer of heat is unfavourable at the 
closed end, where the motion is small. Hence, probably, the advantage of 
the bulb. 
The sounds emitted by a jet of hydrogen burning in an open tube are in 
a measure due to the column of gas in the tube which supplies the jet. If 
this be plugged with cotton, no sound can be obtained. 
When a piece of fine metallic gauze stretched across the lower part of a 
tube open at both ends and held vertically is heated by a gas flame placed 
under it, a sound of considerable power, lasting for several seconds, is 
observed almost immediately after the removal of the flame. It seems to 
be due to a draught impinging on the heated gauze. 
A complementary phenomenon was discovered by Bosscha and Hies. If 
a current of hot air impinge on cold gauze, sound is produced, but, to obtain 
the principal note, the gauze must be in the upper, not in the lower half of 
the tube. 
On the Anatomy of the Organ of Hearing in relation to the Principle of the 
Microphone . — Dr. J. D. Macdonald, F.Ii.S., very ingeniously points out the 
similarity in principle between the vibrating particles of the microphone 
and the otoconia and otoliths in Pteropods, and others of the lower animals. 
Even the malleus and incus in the human ear 11 correspond not only in 
figure, but also in function, to the objects from which their respective 
names are derived, answering very important ends in the faculty of audition.” 
Dr. de Ohaumont notes the influence of moisture as in Mr. Blyth’s experi- 
ments. The otoconia, endolymph, and vestibule of the ear present a complete 
type of a microphone. 
The Electrical Gyroscope . — The value of the gyroscope as a means of 
showing the earth’s rotation independently of any astronomical observation, 
seems hardly to have been appreciated. This, and another noble experiment 
for the same purpose by means of a long pendulum, are due to the ingenuity 
of the late Mons. Foucault. The latter was freely demonstrated at the time of 
its first announcement in many of our large public buildings, especially in the 
Badcliffe Observatory, at Oxford. Its simple relation to the sine of the 
latitude of the place of observation renders it the more valuable. But 
hitherto there has been some difficulty in showingthe more compact form of the 
same physical law which the gyroscope furnishes. Mons. Foucault himself at- 
tained the necessary end of a durable rotation of the heavy disc by means of 
excellent mechanical construction and the avoidance of all unnecessary 
friction. In the Loan Exhibition at South Kensington one of his original 
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