AN IMPROVED CHRONOMETER CALLED "CHRONOSCOPE
Year: 1858

page_text: rotection, ош notice to proceed with
the application for Letters Patent, was not given within the time prescribed
by the Act.)
PROVISIONAL SPECIFICATION left by Joseph Antoine Jean Redier at
the Office of the Commissioners of Patents, with his Petition, on the
18th March 1858.
I, JOSEPH ANTOINE JEAN REDIER, of Paris, in the Empire of France,
Watchmaker, do hereby declare the nature of the said Invention for "AN
IMPROVED CHRONOMETER CALLED "CHRONOSCOPE," to be as follows:-
This instrument, termed a chronoscope, is intended for delicate chro-
nometrical observations in astronomy; it can also be used for experiments
of short duration, and is based on the faculty possessed by the ear of detecting
the coincidence of two shocks. In order to render its construction intelligible
I will refer to an independent seconds watch, such watches being well known.
In these watches the escape wheel has fifteen teeth and a pinion of six
leaves, the escapement is actuated by an ordinary watch train. Another
train of wheels, which carries the large seconds hand, terminates in a fly
which makes exactly one revolution for each sixtieth part of a revolution
made by this seconds hand. The action of this fly is regulated thus:-One.
of its extremities rests on one of the leaves of the pinion of the escape wheel,
and this wheel by revolving causes the fly to effect contact at a point of the
pinion from which it escapes; this fly when free turns, and after having made
rather less than a revolution is stopped by the next leaf of the escapement
pinion, which does not let it again escape until a second of time has elapsed.

page_text: The action continues thus as long as the two trains are acting in concert ;
when the fly falls on the leaf of the pinion it make a peculiar sharp noise,
which is utilized and referred to herein-after. This being understood, the
chronoscope is thus constructed:-Supposing the escape wheel of an ordinary
chronometer train placed exactly at the centre of the plate of the movement,
arrangements are made that on one of the two plates no part should project,
and that the balance may make ten vibrations a second, or fifteen or twenty,
as desired. The pivot of the escape wheel on the side of this plate is
lengthened like a seconds pivot, and if ten vibrations a second are the result
of an escape wheel of fifteen teeth, I adjust on this projecting pivot a three-
toothed star wheel, so that this wheel shall make its revolution in three
seconds, and so that each tooth of the star wheel shall represent one second.
This first movement being made and adjusted in a cylindrical box of copper,
I construct another movement of the same size, and adjust it in a similar
box, which will carry the ordinary train of the independent seconds. Thisy.
latter box, of the same size as the former, is conveniently adjusted thereon, so
that the two superposed movements may move any extent in relation with
each other, which movement can be measured by divisions traced immediately
on one of the boxes. In the case of a three-toothed star wheel this division
would be three large marks to represent the seconds, and ten little marks to
represent tenths of seconds.
I have before said that the upper movement was a train of independent
seconds; it actuates a hand acting on a dial, which marks hours, minutes,
and seconds as usual.
The fly, which always makes one revolution a second, lias its centre towards
the middle of the radius of the plate of its movement, and its extremity is of
such a length and in such position that when the movements are superposed
it stops on the teeth of the three-toothed star wheel. In this state it will be
understood that it is a watch with ordinary independent seconds, with this
difference, that instead of having the two wheel trains on the same planes they
are superposed, but if the upper movement be made to turn at will, relatively to
the lower movement, the upper second hand will thus change the movement of
its escapement and the time of the sharp blow of its train will be changed, and
this is the fundamental principle of the chronoscope..
The following is in fact what would take place:-Supposing that in presence
of a seconds clock the instrument described above strikes the seconds exactly
at the same time as this clock, and that there is perfect coincidence between
the two shocks of the escapement, the chronoscope and clock being both
regulated according to the mean time, this coincidence will not be departed

page_text: from, but by displacing the upper movement a sixth of the circumference it is
evident, that since there are three seconds for one turn of the three toothed star
wheel, the independent seconds will be caused to strike precisely half a second.
sooner or later than it before struck according to the direction in which the
change of position of the two movements takes places. If the movements had
been displaced the thirtieth part of the circumference, the coincidence between
the two seconds would only have differed one-tenth of a second; it will be readily
understood that in order that the shock of the independent seconds may be
made in advance, its movement must be turned in a direction contrary to the
motion of the three-toothed star wheel; and conversely, in order that it may
be later. By repeated trials the relative position of the two movements
which leads to the perfect coincidence of the chronoscope, and a clock or
chronometer can be found to a tenth or a twentieth, &c., of a second. Also if
the upper box is caused to make an entire revolution in the direction of the
three-toothed star wheel its chronoscope will be retarded just three seconds;
if this revolution is made in the opposite direction the chronoscope will
advance exactly three seconds; three revolutions make nine seconds, two
revolutions and four-thirtieths of the circumference would make six seconds.
and four-tenths of advance or retrograde movement according to the direction
in which the upper movement is made. Hence it will be seen that the
important property of this new instrument consists in its faculty of being
placed in perfect accordance with another chronometer, and of giving the
measure of its deviation or difference exactly. Among other purposes to
which it is applicable I will give the two following:-
In an observatory, supposing two clocks to be at a stance apart and it is
desired to know as near as possible the difference of time between these two
clocks, I first make the chronoscope and the first clock coincide perfectly, and
place the moveable index of the chronoscope at zero of the divisions traced on
the circumferences of one of the boxes; I now go to the other clock, and by
turning to the right or left I make the chronoscope coincide perfectly with this
second clock, and the extent which it has been necessary to turn it gives the
exact difference between the two clocks. If after this operation the chrono-
scope be returned to its original position, it is evident that it will again give
the hour of the first clock, and will thus prove that it has acted correctly.
Thus, without calculation and in a few seconds, a very delicate operation can
be performed.
It is known that at sea
The following is a second use of this instrument.
the chronometer for used for ascertaining the longitudes remains in the captain's
cabin while the observations are taken on the deck of the ship. Now there is

page_text: no means of indicating with sufficient exactitude on deck the hour of the chono-
meter; this chronoscope will fulfil this duty perfectly. The chronoscope is
set exactly with the chronometer, and if from any cause the former should
not be regulated exactly, as these observations last but a few minutes, it
itself serves to measure the variation exactly, and renders these important
observations sure and easy. This instrument may be constructed with some
modifications of that above referred to, but the principle in all cases is the
same. For instance, instead of a star wheel with the teeth fixed on the
projecting pivot of the escape wheel of the lower movement, a five-
toothed star wheel may be used. In this case an entire revolution of the
upper movement produces five seconds of advance or retrograde movement,
which would be easier to count. Nothing further would be required than to
regulate the beats of the balance and the number of the teeth of the escapement
wheel accordingly. It will be understood that the greater the number of the
beats the nearer will be the approximation, and I construct chronoscopes in
which I cause a small anchor to beat fifty times a second; the action of this
small anchor is regulated by a third chronometer placed in the same box in
the same manner as that made by Mr. Wagner, of Paris, for obtaining the
continuous movement in his clocks. It must be understood that I can cause
the same instrument to strike the half second, and can introduce the whole
second or half second in the same apparatus.
In the example herein-before described it suffices to place a six-toothed
star wheel above the three-toothed star wheel, and to introduce two stops
diametrically opposed to the fly; by pressing on a knob the two stops can be
made to press each in its turn on the six-toothed star wheel, and in this case
I have the half second, or the longer one of the two can be made to stop on
the three-toothed star only, and then I have the second, as before described.