shown. The bar for suspending the coil plates so made in the cells is
soldered to the coil. The object of this construction is of course to
obtain large lead surface, and of course a much larger surface is so
obtained than could be practically obtained from plain lead plates in
the same compass. A battery thus made may be seen at the offices of the
company, 110 Cannon Street.

[Illustration: FIG. 1. FIG. 2.]

A very ingenious device for cutting the battery out of circuit when
charged as much as is thought desirable is used by the company. In a
cell is an element which has a determined lower capacity than those in
the rest of the battery. Over this element is placed a gas-tight chamber
in which is a diaphgram, this diaphragm being of very flexible material
placed in the cover of the box of cells. When charging has proceeded as
long as is desirable, or proceeds too fast, hydrogen is evolved, and
this collecting in the chamber referred to acts upon the diaphragm, and
by means of a rod connected thereto, switches the current, which is
supplied to an electro-magnet and by which circuit is made through the
medium of mercury contacts. The object, of this is to save the
battery from destruction by over-charging or charging by too large a
current.--_The Engineer_.

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ACETYLENE FROM IODOFORM.