near J. The ball will be quickly repelled, and care must be taken that
it does not come into contact with J. After this the apparatus is placed
upon a table, the shell, S, is taken by its handle, G, and placed in the
position shown in the figure, and a momentary contact is established
between the two hemispheres by pressing the button, K. Then the shell,
S, is lifted, and the disk, M, is touched at the same time with the
other hand. If, now, the pith ball be brought near S, it will be quickly
repelled, while it will remain stationary if it be brought near J, thus
proving that all the electricity passed from J to S at the moment of
contact.--_La Lumiere Electrique_.

* * * * *




THE COLSON TELEPHONE.


This apparatus has recently been the object of some experiments which
resulted in its being finally adopted in the army. We think that our
readers will read a description of it with interest. Its mode of
construction is based upon a theoretic conception of the lines of force,
which its inventor explains as follows in his Elementary Treatise on
Electricity:

"To every position of the disk of a magnetic telephone with respect to
the poles of the magnet there corresponds a certain distribution of the
lines of force, which latter shift themselves when the disk is
vibrating. If the bobbin be met by these lines in motion, there will