eing the same as in Fig.
1. As to the additional reference letters, I is a condenser J the source
of light, and K a reflector.

The positive film is moved intermittently but swiftly throughout its
length between the objective lens and a beam of light coming through the
condenser, being exposed by the shutter during the periods of rest. This
results in a projection of the photographs upon a screen in such rapid
succession as to present an apparently continuous photograph of the
successive positions of the moving objects, which, therefore, appear to
the human eye to be in motion.

The first claim of Reissue Patent No. 12,192 describes the film. It
reads as follows:

"An unbroken transparent or translucent tape-like photographic film
having thereon uniform, sharply defined, equidistant photographs of
successive positions of an object in motion as observed from a single
point of view at rapidly recurring intervals of time, such photographs
being arranged in a continuous straight-line sequence, unlimited in
number save by the length of the film, and sufficient in number to
represent the movements of the object throughout an extended period of
time."

XVI. EDISON'S ORE-MILLING INVENTIONS

THE wide range of Edison's activities in this department of the arts is
well represented in the diversity of the numerous patents that have been
issued to him from time to time. These patents are between fifty and
sixty in number, and include magnetic ore separators of ten distinct
types; also breaking, crushing, and grinding rolls, conveyors,
dust-proof bearings, screens, driers, mixers, bricking apparatus and
machines, ovens, and processes of various kinds.

A description of the many devices in each of these divisions would
require more space than is available; hence, we shall confine ourselves
to a few items of predominating importance, already referred to in the
narrative, commencing with the fundamental magnetic ore separator, which
was covered by United States Patent No. 228,329, issued June 1, 1880.

The illustration here presented is copied from the drawing forming part
of this patent. A hopper with adjustable feed is supported several feet
above a bin having a central partition. Almost midway between the hopper
and the bin is placed an electromagnet whose polar extension is so
arranged as to be a little to one side of a stream of material falling
from the hopper. Normally, a stream of finely divided ore falling from