The Electromagnet Separates Iron Ore
In his study of the Crown Point Iron Industry, Dr. Eugene Barker
writes about the separating of iron from ore.
" The ore, after being mined, was drawn to large open
kilns, about 300 tons of it being piled upon twenty-five cords of wood. Heat
caused the stone to loose its hold from the iron. The ore was then generally
put through the water process of separation. It was placed in troughs with grate
bottoms, in which it was stumped and screened, the passed through sieves through
which water rose from the bottom. The iron being heavier, sank through holes
in the bottom of the sieve into a trough, while the pulverized rock was raised
and carried off by the current of the water, often together with a considerable
amount of the iron in fine particles."
This was a wasteful process and so a separator came to be used
in Crown Point. It was a cylinder about 5 feet in length and 2 1/2 feet in diameter
studded with magnetized bars on its surface. It revolved in a trough into which
ore was shoveled. The iron particles were attracted to the magnetic charge of
the bars and came out of the trough on them as the cylinder revolved. Stationary
brushes then wiped the bars clean and the iron fell into waiting receptacles.
After awhile the magnetic bars would lose strength and need to be re-charged
by the electromagnet.
He goes on to say that the electromagnet in use at Crown Point
was secured in 1831 from Professor Henry of the Albany Academy at Albany, NY
(who later became Director of the Smithsonian Museum). It was worked by a galvanic
cell (wet battery) for recharging the bar magnets of the separator and for detecting
iron and steel from brass and copper scrap metal.