rs of the spark produced by induction coils
on the machines so improperly called "static." Finally, we may cite
the apparatus arranged by Mr. S.P. Thompson for studying the
development of currents in magneto-electric machines. The inventor
studies the influence of the forms of the inductors and armatures of
machines by means of an arrangement that allows him to change the
rings or armatures at will and to take out the induced bobbins in
order to sound every part of the magnetic field. Upon giving the
armature an angular motion limited by two stops, there develops a
certain quantity of electricity that may be measured by causing it to
traverse an appropriate ballistic galvanometer. Messrs. Deprez and
D'Arsonval's galvanometer answers very well for this purpose, and its
aperiodicity, which causes it quickly to return to zero as soon as the
induced current ceases, permits of a large number of readings being
taken within a very short space of time.

Measuring apparatus were represented by a new and very elegant
arrangement of Sir William Thomson's reflecting galvanometers, due to
Mr. J. Carpentier. The mounting adopted by Mr. Carpentier permits of
an easy removal of the bobbins and of an instantaneous substitution
therefor. The galvanometric part, composed of the needles and mirror,
therefore remains entirely free, thus allowing of its being verified,
and making it convenient to attach the silken fiber. Mr. Carpentier
has, moreover, adopted for all the minor apparatus a transparent
celluloid scale which simplifies them, facilitates observations, and
renders the use of reflection almost industrial.

We shall complete our enumeration of the measuring apparatus by citing
Ducretet's non-oscillating galvanometer, Sir William Thomson's
amperemeters, voltameters, ohmmeters, and mhosmeters, constructed and
exhibited by Breguet, and a new aperiodic galvanoscope of Mr. Maiche.
Mr. Baudot exhibited the recent improvements that he has made in his
multiplex printing telegraph, and M. Boudet of Paris showed a new
system of telephone transmission by submarine cables.

[Illustration: FIG. 1.--DIAGRAM EXHIBITING THE ARRANGEMENT FOR
TELEPHONIC TRANSMISSIONS WITHOUT A RECEIVER.]

Finally, we shall conclude our enumeration by referring to the
curiosities. The house of Siemens exhibited a miniature electric
railway actuated by a new model of Reynier accumulators; M. Maiche
operated a system of musical telephonic auditions that differed only