Bauhaus-Universität Weimar

Titel:
Note on the electro-magnetic chronoscope
Person:
Wheatstone, [Charles]
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit29405/6/
Wheatstone on the Electro-Magnetic Chronoscope. 91 
division was obtained by dividing the time of the entire fall 
by the number of divisions passed over in this interval; but 
methods still more exact may be employed. 
By means of this instrument, I have measured the time 
occupied by a pistol ball in traversing different ranges, with 
different charges of powder. The repetition of these experi¬ 
ments gave out results that were very constant, rarely present¬ 
ing a difference of more than one division of the chronoscope.* 
1 also measured the fall of a ball from different heights; and 
the law of accelerated velocities was obtained with mathema¬ 
tical rigour. With the apparatus that I employed for this 
latter experiment, I could measure the fall of a ball from the 
height of an inch. It would be difficult, without the assistance 
of drawings, to give an idea of the different arrangements 
that I have adopted to render the instrument applicable to 
different series of experiments ; but I may mention that, 
among the applications, I propose to employ it for measuring 
the velocity of sound through air, water, and masses of 
rock, with an approximation that has never been obtained 
heretofore 
Independently of the instrument which I furnished to M. 
de KonstantinofF, in April, 1843, Prof. Christie deposited one 
in the Museum of Natural Philosophy of the Military Academy 
at Woolwich ; and another was made for Mr. R. Addams, 
who has since constantly used it in his lectures at the United 
Service Museumf and elsewhere. 
I will mention a modification of the instrument that is im¬ 
portant for certain series of experiments :—instead of breaking 
the continuity of the circuit, and re-establishing it imme¬ 
diately, as we have hitherto said, the electro-magnet is main¬ 
tained in equilibrio by means of two equal and opposite 
currents; on interrupting the first circuit the equilibrium is 
destroyed; and on interrupting the second the current occa¬ 
sioned by the interruption of the equilibrium ceases. The 
second ci i cuit is broken by a ball traversing a frame, on 
which is s retched a very fine wire arranged in parallel lines 
very clos to each other, and forming part of the circuit. 
This arrangement furnishes means for employing a chrono¬ 
scope totally different from the former. Two pendulums, one 
a half-sec nd pendulum, and the other having a little more ac¬ 
celerated îotior, are each maintained at the extremities of their 
* These < , périmé ats, in which I was assisted by Sir James South and Mr. 
Purday, th<_ celebrated gunsmith, took place in October, 1842, in the grounds 
belonging to the observatory at Camden Hill. 
f Vide Ehe. Mag., vol. i., p. 473, which refers to the instrument «een at the 
United Serv e Museum.
        

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