have realized the full meaning of the tremendous problems
involved.

From 1880 to 1885, while still very busy in the development of his
electric-light system, Edison found opportunity to plan crushing and
separating machinery. His first patent on the subject was applied for
and issued early in 1880. He decided, after mature deliberation, that
the magnetic separation of low-grade ores on a colossal scale at a low
cost was the only practical way of supplying the furnace-man with a high
quality of iron ore. It was his opinion that it was cheaper to quarry
and concentrate lean ore in a big way than to attempt to mine, under
adverse circumstances, limited bodies of high-grade ore. He appreciated
fully the serious nature of the gigantic questions involved; and his
plans were laid with a view to exercising the utmost economy in the
design and operation of the plant in which he contemplated the automatic
handling of many thousands of tons of material daily. It may be stated
as broadly true that Edison engineered to handle immense masses of stuff
automatically, while his predecessors aimed chiefly at close separation.

Reduced to its barest, crudest terms, the proposition of magnetic
separation is simplicity itself. A piece of the ore (magnetite) may be
reduced to powder and the ore particles separated therefrom by the help
of a simple hand magnet. To elucidate the basic principle of Edison's
method, let the crushed ore fall in a thin stream past such a magnet.
The magnetic particles are attracted out of the straight line of the
falling stream, and being heavy, gravitate inwardly and fall to one
side of a partition placed below. The non-magnetic gangue descends in
a straight line to the other side of the partition. Thus a complete
separation is effected.

Simple though the principle appears, it was in its application to vast
masses of material and in the solving of great engineering problems
connected therewith that Edison's originality made itself manifest in
the concentrating works that he established in New Jersey, early in the
nineties. Not only did he develop thoroughly the refining of the crushed
ore, so that after it had passed the four hundred and eighty magnets
in the mill, the concentrates came out finally containing 91 to 93 per
cent. of iron oxide, but he also devised collateral machinery, methods
and processes all fundamental in their nature. These are too numerous to
specify in detail, as they extended throughou