226 
MINUTES OF PROCEEDINGS OF 
APPENDIX. 
Description of the electro-ballistic chronoscope, exhibited and explained 
before the Boyal Artillery Institution by Professor Charles Wheatstone, 
P.B.S., 17th July, 1841. Extracted from the unpublished Proceedings of 
the Institution 
“The first hand of the instrument makes 73 revolutions in a second of time; 
and as the dial is divided into 100 equal parts, the °f a second (*000137 sec.) 
is indicated. 
“The second hand performs one revolution while the first makes ten, and in 
like manner the third hand performs one revolution while the second makes ten. 
Thus 10,000 units of time are registered, each unit being, as above stated, 7 -jVo 
of a second. 
“ The expense of this instrument (the first that has been made) has been £10 ; a 
more accurate one might be made for £20. The gun and butt being provided, 
about £5 would defray the expense of adapting the instrument to projectile experi¬ 
ments. 
“In an instrument so totally new as mine, many proof experiments will be 
required, and probably some alterations in the construction, before its minute 
indications can be relied upon; but the principle is capable of great accuracy, and 
I am confident that, when everything is properly arranged, the error in a single 
observation would not attain the -jpoTr P ai 't °f a secon d. 
“ Perhaps an instrument which would record the time in tenths of seconds, and 
in which the error in a single observation should not attain the tenth of a second, 
would be sufficient for most practical purposes. I could construct such an instru¬ 
ment, which would require no proof experiments, and could be used by any person 
with ordinary care. 
“ The chronoscope for measuring the duration of flashes, such as those produced 
by the ignition of powder, is an instrument constructed on a principle entirely 
different from the preceding. By its means the Tir Jy-g- part of a second may be 
estimated.” 
Such was the description given by Sir Charles Wheatstone of his chrono¬ 
scope in 1841. The instrument of 1857 so far resembled it that it was 
also a delicate clock movement, started and stopped by successively breaking 
two currents, as already described in the text; but it differed in its details. 
An account of the latter has been given by Professor Pepper, of the Poly¬ 
technic Institution, in one of his popular works, and a similar one was 
employed by Mr. Mallet in his experiments on the rate of transmission of 
earthquake waves. Sir Charles Wheatstone has not published it. 
