Edison, His Life and Inventions [185]
was suffering a disastrous change, and that business was slowly drifting westward, chiefly by reason of the discovery and opening up of enormous deposits of high-grade iron ore in the upper peninsula of Michigan. This ore could be excavated very cheaply by means of improved mining facilities, and transported at low cost to lake ports. Hence the iron and steel mills east of the Alleghanies--compelled to rely on limited local deposits of Bessemer ore, and upon foreign ores which were constantly rising in value--began to sustain a serious competition with Western mills, even in Eastern markets.
Long before this situation arose, it had been recognized by Eastern iron-masters that sooner or later the deposits of high-grade ore would be exhausted, and, in consequence, there would ensue a compelling necessity to fall back on the low-grade magnetic ores. For many years it had been a much-discussed question how to make these ores available for transporta- tion to distant furnaces. To pay railroad charges on ores carrying perhaps 80 to 90 per cent. of useless material would be prohibitive. Hence the elimination of the worthless "gangue" by concentration of the iron particles associated with it, seemed to be the only solution of the problem.
Many attempts had been made in by-gone days to concentrate the iron in such ores by water processes, but with only a partial degree of success. The impossibility of obtaining a uniform concentrate was a most serious objection, had there not indeed been other difficulties which rendered this method commercially impracticable. It is quite natural, therefore, that the idea of magnetic separation should have occurred to many inventors. Thus we find numerous instances throughout the last century of experiments along this line; and particularly in the last forty or fifty years, during which various attempts have been made by others than Edison to perfect magnetic separation and bring it up to something like commercial practice. At the time he took up the matter, however, no one seems to 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 furnaceman 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,
Long before this situation arose, it had been recognized by Eastern iron-masters that sooner or later the deposits of high-grade ore would be exhausted, and, in consequence, there would ensue a compelling necessity to fall back on the low-grade magnetic ores. For many years it had been a much-discussed question how to make these ores available for transporta- tion to distant furnaces. To pay railroad charges on ores carrying perhaps 80 to 90 per cent. of useless material would be prohibitive. Hence the elimination of the worthless "gangue" by concentration of the iron particles associated with it, seemed to be the only solution of the problem.
Many attempts had been made in by-gone days to concentrate the iron in such ores by water processes, but with only a partial degree of success. The impossibility of obtaining a uniform concentrate was a most serious objection, had there not indeed been other difficulties which rendered this method commercially impracticable. It is quite natural, therefore, that the idea of magnetic separation should have occurred to many inventors. Thus we find numerous instances throughout the last century of experiments along this line; and particularly in the last forty or fifty years, during which various attempts have been made by others than Edison to perfect magnetic separation and bring it up to something like commercial practice. At the time he took up the matter, however, no one seems to 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 furnaceman 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,