82
Electrical Magazine.
The problem was this:—to arrange an instrument which
might indicate and preserve thirty or forty successive obser¬
vations, made in very close spaces of time, of a phenomenon
happening at a greater or less distance from the place where
the instrument of observation is situated. It naturally oc¬
curred to us to employ electricity for this purpose.
It was furthermore necessary to unite to this physical part
the mechanical part, which might become very complicated,
but which, however, was not so much so as the solution in
question induced us to presume.
Private reasons had prevented my making this machine
known ; but, as at present nothing remains to prevent its pub¬
licity, I will endeavour to convey as exact an idea of it as I
possibly Can without the aid of figures ; moreover, it has been
seen by MM. Arago, llegnault, and Morin, whose authority
may be quoted if necessary to establish what I advance. M.
Régnault especially has, so to speak, followed it in ail its
phases, and has assisted at almost all the experimental essays
that had in view the verification of the principles on which it
was established.
We thought of employing an apparatus with a revolving
plate, similar to that of M. Morin ; and as we required
several successive indications distant from each other, we had
thought of making the style alter its position, by approaching
or withdrawing from the centre at each new mark ; but this
means did not appear to us sufficient, in that the marks made
at the centre and those made at the circumference were not
within the same limits of error ; for the smaller the radius
was of the arc traced by the style, the greater would be the
chance of error.
We then placed the indications in identical positiom. by
constructing a cylinder of sufficient length to make foi y or
fifty distinct observations, all of which should apperta • to
the same radius. In June, 1843, we commenced the jon-
struction of our machine, which was not completed until
May, 1844.
The following is its arrangement : —
The apparatus is mounted on a cast-iron frame, and is com¬
posed of six distinct parts : —
1st. Of a system of toothed wheels, set in motion by a cord
rolled round a cylinder, and to which is suspended the
moving weight.
2nd. Of a cylinder, 1 metre (3-28 ft.) in circumference, and
0*36 metre (T18 ft.) in length, divided on its surface into a
thousand parts, which are therefore millimetres. In order to
diminish its friction on the pivots, it is supported by a system