and faithful telegraphist.

This regulation, by very small and short successive steps, offers
several advantages: (1) it is imperceptible to the eye; (2) it does not
affect the main current; (3) any sudden instantaneous variation of the
main current does not allow a too near approach of the carbon points.
Let, now, an accident occur; for instance, a carbon is broken. At once
the automatic cut-off acts, the current passes through the resistance,
R, instead of passing through the lamp. The current through the fine
coil is suddenly increased, the rod is drawn in, contact is made at G
and K, and the current is sent through the coil, R. As soon as contact
is again made by the carbons, the current in the coil, S, is increased,
that of the thick wire in V diminished, and the antagonistic spring,
U, breaks the contact at G and K. The rupture of the light is almost
invisible, because the relighting is so brisk and sharp.

I have seen this lamp in action, and its constant steadiness leaves
nothing to be desired.

* * * * *




APPARATUS FOR OBTAINING PURE WATER FOR PHOTOGRAPHIC USE.


Our readers are well aware that water as found naturally is never
absolutely free from dissolved impurities; and in ordinary cases it
contains solid impurities derived both from the inorganic and organic