Things went fairly well for a time on that memorable Thursday afternoon, when all the laboratory force made high holiday and scrambled for foothold on the locomotive for a trip; but the friction gearing was not equal to the sudden strain put upon it during one run and went to pieces. Some years later, also, Daft again tried friction gear in his historical experiments on the Manhattan Elevated road, but the results were attended with no greater success. The next resort of Edison was to belts, the armature shafting belted to a countershaft on the locomotive frame, and the countershaft belted to a pulley on the car-axle. The lever which threw the former friction gear into adjustment was made to operate an idler pulley for tightening the axle-belt. When the motor was started, the armature was brought up to full revolution and then the belt was tightened on the car-axle, compelling motion of the locomotive.

But the belts were liable to slip a great deal in the process, and the chafing of the belts charred them badly. If that did not happen, and if the belt was made taut suddenly, the armature burned out--which it did with disconcerting frequency. The next step was to use a number of resistance-boxes in series with the armature, so that the locomotive could start with those in circuit, and then the motorman could bring it up to speed gradually by cutting one box out after the other. To stop the locomotive, the armature circuit was opened by the main switch, stopping the flow of current, and then brakes were applied by long levers. Matters generally and the motors in particular went much better, even if the locomotive was so freely festooned with resistance-boxes all of perceptible weight and occupying much of the limited s.p.a.ce. These details show forcibly and typically the painful steps of advance that every inventor in this new field had to make in the effort to reach not alone commercial practicability, but mechanical feasibility. It was all empirical enough; but that was the only way open even to the highest talent.

Smugglers landing laces and silks have been known to wind them around their bodies, as being less ostentatious than carrying them in a trunk.

Edison thought his resistance-boxes an equally superfluous display, and therefore ingeniously wound some copper resistance wire around one of the legs of the motor field magnet, where it was out of the way, served as a useful extra field coil in starting up the motor, and dismissed most of the boxes back to the laboratory--a few being retained under the seat for chance emergencies. Like the boxes, this coil was in series with the armature, and subject to plugging in and out at will by the motorman. Thus equipped, the locomotive was found quite satisfactory, and long did yeoman service. It was given three cars to pull, one an open awning-car with two park benches placed back to back; one a flat freight-car, and one box-car dubbed the "Pullman," with which Edison ill.u.s.trated a system of electric braking. Although work had been begun so early in the year, and the road had been operating since May, it was not until July that Edison executed any application for patents on his "electromagnetic railway engine," or his ingenious braking system. Every inventor knows how largely his fate lies in the hands of a competent and alert patent attorney, in both the preparation and the prosecution of his case; and Mr. Sprague is justified in observing in his Century article: "The paucity of controlling claims obtained in these early patents is remarkable." It is notorious that Edison did not then enjoy the skilful aid in safeguarding his ideas that he commanded later.

The daily newspapers and technical journals lost no time in bringing the road to public attention, and the New York Herald of June 25th was swift to suggest that here was the locomotive that would be "most pleasing to the average New Yorker, whose head has ached with noise, whose eyes have been filled with dust, or whose clothes have been ruined with oil." A couple of days later, the Daily Graphic ill.u.s.trated and described the road and published a sketch of a one-hundred-horse-power electric locomotive for the use of the Pennsylvania Railroad between Perth Amboy and Rahway. Visitors, of course, were numerous, including many curious, sceptical railroad managers, few if any of whom except Villard could see the slightest use for the new motive power. There is, perhaps, some excuse for such indifference. No men in the world have more new inventions brought to them than railroad managers, and this was the rankest kind of novelty. It was not, indeed, until a year later, in May, 1881, that the first regular road collecting fares was put in operation--a little stretch of one and a half miles from Berlin to Lichterfelde, with one miniature motorcar. Edison was in reality doing some heavy electric-railway engineering, his apparatus full of ideas, suggestions, prophecies; but to the operators of long trunk lines it must have seemed utterly insignificant and "excellent fooling."

Speaking of this situation, Mr. Edison says: "One day Frank Thomson, the President of the Pennsylvania Railroad, came out to see the electric light and the electric railway in operation. The latter was then about a mile long. He rode on it. At that time I was getting out plans to make an electric locomotive of three hundred horse-power with six-foot drivers, with the idea of showing people that they could dispense with their steam locomotives. Mr. Thomson made the objection that it was impracticable, and that it would be impossible to supplant steam. His great experience and standing threw a wet blanket on my hopes. But I thought he might perhaps be mistaken, as there had been many such instances on record. I continued to work on the plans, and about three years later I started to build the locomotive at the works at Goerck Street, and had it about finished when I was switched off on some other work. One of the reasons why I felt the electric railway to be eminently practical was that Henry Villard, the President of the Northern Pacific, said that one of the greatest things that could be done would be to build right-angle feeders into the wheat-fields of Dakota and bring in the wheat to the main lines, as the farmers then had to draw it from forty to eighty miles. There was a point where it would not pay to raise it at all; and large areas of the country were thus of no value.

I conceived the idea of building a very light railroad of narrow gauge, and had got all the data as to the winds on the plains, and found that it would be possible with very large windmills to supply enough power to drive those wheat trains."

Among others who visited the little road at this juncture were persons interested in the Manhattan Elevated system of New York, on which experiments were repeatedly tried later, but which was not destined to adopt a method so obviously well suited to all the conditions until after many successful demonstrations had been made on elevated roads elsewhere. It must be admitted that Mr. Edison was not very profoundly impressed with the desire entertained in that quarter to utilize any improvement, for he remarks: "When the Elevated Railroad in New York, up Sixth Avenue, was started there was a great clamor about the noise, and injunctions were threatened. The management engaged me to make a report on the cause of the noise. I constructed an instrument that would record the sound, and set out to make a preliminary report, but I found that they never intended to do anything but let the people complain."

It was upon the co-operation of Villard that Edison fell back, and an agreement was entered into between them on September 14, 1881, which provided that the latter would "build two and a half miles of electric railway at Menlo Park, equipped with three cars, two locomotives, one for freight, and one for pa.s.sengers, capacity of latter sixty miles an hour. Capacity freight engine, ten tons net freight; cost of handling a ton of freight per mile per horse-power to be less than ordinary locomotive.... If experiments are successful, Villard to pay actual outlay in experiments, and to treat with the Light Company for the installation of at least fifty miles of electric railroad in the wheat regions." Mr. Edison is authority for the statement that Mr. Villard advanced between $35,000 and $40,000, and that the work done was very satisfactory; but it did not end at that time in any practical results, as the Northern Pacific went into the hands of a receiver, and Mr.

Villard's ability to help was hopelessly crippled. The directors of the Edison Electric Light Company could not be induced to have anything to do with the electric railway, and Mr. Insull states that the money advanced was treated by Mr. Edison as a personal loan and repaid to Mr. Villard, for whom he had a high admiration and a strong feeling of attachment. Mr. Insull says: "Among the financial men whose close personal friendship Edison enjoyed, I would mention Henry Villard, who, I think, had a higher appreciation of the possibilities of the Edison system than probably any other man of his time in Wall Street. He dropped out of the business at the time of the consolidation of the Thomson-Houston Company with the Edison General Electric Company; but from the earliest days of the business, when it was in its experimental period, when the Edison light and power system was but an idea, down to the day of his death, Henry Villard continued a strong supporter not only with his influence, but with his money. He was the first capitalist to back individually Edison's experiments in electric railways."

In speaking of his relationships with Mr. Villard at this time, Edison says: "When Villard was all broken down, and in a stupor caused by his disasters in connection with the Northern Pacific, Mrs. Villard sent for me to come and cheer him up. It was very difficult to rouse him from his despair and apathy, but I talked about the electric light to him, and its development, and told him that it would help him win it all back and put him in his former position. Villard made his great rally; he made money out of the electric light; and he got back control of the Northern Pacific. Under no circ.u.mstances can a hustler be kept down. If he is only square, he is bound to get back on his feet. Villard has often been blamed and severely criticised, but he was not the only one to blame.

His engineers had spent $20,000,000 too much in building the road, and it was not his fault if he found himself short of money, and at that time unable to raise any more."

Villard maintained his intelligent interest in electric-railway development, with regard to which Edison remarks: "At one time Mr.

Villard got the idea that he would run the mountain division of the Northern Pacific Railroad by electricity. He asked me if it could be done. I said: 'Certainly, it is too easy for me to undertake; let some one else do it.' He said: 'I want you to tackle the problem,' and he insisted on it. So I got up a scheme of a third rail and shoe and erected it in my yard here in Orange. When I got it all ready, he had all his division engineers come on to New York, and they came over here.

I showed them my plans, and the unanimous decision of the engineers was that it was absolutely and utterly impracticable. That system is on the New York Central now, and was also used on the New Haven road in its first work with electricity."

At this point it may be well to cite some other statements of Edison as to kindred work, with which he has not usually been a.s.sociated in the public mind. "In the same manner I had worked out for the Manhattan Elevated Railroad a system of electric trains, and had the control of each car centred at one place--multiple control. This was afterward worked out and made practical by Frank Sprague. I got up a slot contact for street railways, and have a patent on it--a sliding contact in a slot. Edward Lauterbach was connected with the Third Avenue Railroad in New York--as counsel--and I told him he was making a horrible mistake putting in the cable. I told him to let the cable stand still and send electricity through it, and he would not have to move hundreds of tons of metal all the time. He would rue the day when he put the cable in."

It cannot be denied that the prophecy was fulfilled, for the cable was the beginning of the frightful financial collapse of the system, and was torn out in a few years to make way for the triumphant "trolley in the slot."

Incidental glimpses of this work are both amusing and interesting.

Hughes, who was working on the experimental road with Mr. Edison, tells the following story: "Villard sent J. C. Henderson, one of his mechanical engineers, to see the road when it was in operation, and we went down one day--Edison, Henderson, and I--and went on the locomotive.

Edison ran it, and just after we started there was a trestle sixty feet long and seven feet deep, and Edison put on all the power. When we went over it we must have been going forty miles an hour, and I could see the perspiration come out on Henderson. After we got over the trestle and started on down the track, Henderson said: 'When we go back I will walk.

If there is any more of that kind of running I won't be in it myself.'"

To the correspondence of Grosvenor P. Lowrey we are indebted for a similar reminiscence, under date of June 5, 1880: "G.o.ddard and I have spent a part of the day at Menlo, and all is glorious. I have ridden at forty miles an hour on Mr. Edison's electric railway--and we ran off the track. I protested at the rate of speed over the sharp curves, designed to show the power of the engine, but Edison said they had done it often.

Finally, when the last trip was to be taken, I said I did not like it, but would go along. The train jumped the track on a short curve, throwing Kruesi, who was driving the engine, with his face down in the dirt, and another man in a comical somersault through some underbrush.

Edison was off in a minute, jumping and laughing, and declaring it a most beautiful accident. Kruesi got up, his face bleeding and a good deal shaken; and I shall never forget the expression of voice and face in which he said, with some foreign accent: 'Oh! yes, pairf.e.c.kly safe.'

Fortunately no other hurts were suffered, and in a few minutes we had the train on the track and running again."

All this rough-and-ready dealing with grades and curves was not mere horse-play, but had a serious purpose underlying it, every trip having its record as to some feature of defect or improvement. One particular set of experiments relating to such work was made on behalf of visitors from South America, and were doubtless the first tests of the kind made for that continent, where now many fine electric street and interurban railway systems are in operation. Mr. Edison himself supplies the following data: "During the electric-railway experiments at Menlo Park, we had a short spur of track up one of the steep gullies. The experiment came about in this way. Bogota, the capital of Columbia, is reached on muleback--or was--from Honda on the headwaters of the Magdalena River.

There were parties who wanted to know if transportation over the mule route could not be done by electricity. They said the grades were excessive, and it would cost too much to do it with steam locomotives, even if they could climb the grades. I said: 'Well, it can't be much more than 45 per cent.; we will try that first. If it will do that it will do anything else.' I started at 45 per cent. I got up an electric locomotive with a grip on the rail by which it went up the 45 per cent.

grade. Then they said the curves were very short. I put the curves in.

We started the locomotive with n.o.body on it, and got up to twenty miles an hour, taking those curves of very short radius; but it was weeks before we could prevent it from running off. We had to bank the tracks up to an angle of thirty degrees before we could turn the curve and stay on. These Spanish parties were perfectly satisfied we could put in an electric railway from Honda to Bogota successfully, and then they disappeared. I have never seen them since. As usual, I paid for the experiment."

In the spring of 1883 the Electric Railway Company of America was incorporated in the State of New York with a capital of $2,000,000 to develop the patents and inventions of Edison and Stephen D. Field, to the latter of whom the practical work of active development was confided, and in June of the same year an exhibit was made at the Chicago Railway Exposition, which attracted attention throughout the country, and did much to stimulate the growing interest in electric-railway work. With the aid of Messrs. F. B. Rae, C. L. Healy, and C. O. Mailloux a track and locomotive were constructed for the company by Mr. Field and put in service in the gallery of the main exhibition building. The track curved sharply at either end on a radius of fifty-six feet, and the length was about one-third of a mile. The locomotive named "The Judge," after Justice Field, an uncle of Stephen D. Field, took current from a central rail between the two outer rails, that were the return circuit, the contact being a rubbing wire brush on each side of the "third rail," answering the same purpose as the contact shoe of later date. The locomotive weighed three tons, was twelve feet long, five feet wide, and made a speed of nine miles an hour with a trailer car for pa.s.sengers. Starting on June 5th, when the exhibition closed on June 23d this tiny but typical road had operated for over 118 hours, had made over 446 miles, and had carried 26,805 pa.s.sengers. After the exposition closed the outfit was taken during the same year to the exposition at Louisville, Kentucky, where it was also successful, carrying a large number of pa.s.sengers. It deserves note that at Chicago regular railway tickets were issued to paying pa.s.sengers, the first ever employed on American electric railways.

With this modest but brilliant demonstration, to which the ill.u.s.trious names of Edison and Field were attached, began the outburst of excitement over electric railways, very much like the eras of speculation and exploitation that attended only a few years earlier the introduction of the telephone and the electric light, but with such significant results that the capitalization of electric roads in America is now over $4,000,000,000, or twice as much as that of the other two arts combined. There was a tremendous rush into the electric-railway field after 1883, and an outburst of inventive activity that has rarely, if ever, been equalled. It is remarkable that, except Siemens, no European achieved fame in this early work, while from America the ideas and appliances of Edison, Van Depoele, Sprague, Field, Daft, and Short have been carried and adopted all over the world.

Mr. Edison was consulting electrician for the Electric Railway Company, but neither a director nor an executive officer. Just what the trouble was as to the internal management of the corporation it is hard to determine a quarter of a century later; but it was equipped with all essential elements to dominate an art in which after its first efforts it remained practically supine and useless, while other interests forged ahead and reaped both the profit and the glory. Dissensions arose between the representatives of the Field and Edison interests, and in April, 1890, the Railway Company a.s.signed its rights to the Edison patents to the Edison General Electric Company, recently formed by the consolidation of all the branches of the Edison light, power, and manufacturing industry under one management. The only patent rights remaining to the Railway Company were those under three Field patents, one of which, with controlling claims, was put in suit June, 1890, against the Jamaica & Brooklyn Road Company, a customer of the Edison General Electric Company. This was, to say the least, a curious and anomalous situation. Voluminous records were made by both parties to the suit, and in the spring of 1894 the case was argued before the late Judge Townsend, who wrote a long opinion dismissing the bill of complaint. [15] The student will find therein a very complete and careful study of the early electric-railway art. After this decision was rendered, the Electric Railway Company remained for several years in a moribund condition, and on the last day of 1896 its property was placed in the hands of a receiver. In February of 1897 the receiver sold the three Field patents to their original owner, and he in turn sold them to the Westinghouse Electric and Manufacturing Company. The Railway Company then went into voluntary dissolution, a sad example of failure to seize the opportunity at the psychological moment, and on the part of the inventor to secure any adequate return for years of effort and struggle in founding one of the great arts. Neither of these men was squelched by such a calamitous result, but if there were not something of bitterness in their feelings as they survey what has come of their work, they would not be human.

As a matter of fact, Edison retained a very lively interest in electric-railway progress long after the pregnant days at Menlo Park, one of the best evidences of which is an article in the New York Electrical Engineer of November 18, 1891, which describes some important and original experiments in the direction of adapting electrical conditions to the larger cities. The overhead trolley had by that time begun its victorious career, but there was intense hostility displayed toward it in many places because of the inevitable increase in the number of overhead wires, which, carrying, as they did, a current of high voltage and large quant.i.ty, were regarded as a menace to life and property. Edison has always manifested a strong objection to overhead wires in cities, and urged placing them underground; and the outcry against the overhead "deadly" trolley met with his instant sympathy.

His study of the problem brought him to the development of the modern "substation," although the twists that later evolutions have given the idea have left it scarcely recognizable.

[Footnote 15: See 61 Fed. Rep. 655.]

Mr. Villard, as President of the Edison General Electric Company, requested Mr. Edison, as electrician of the company, to devise a street-railway system which should be applicable to the largest cities where the use of the trolley would not be permitted, where the slot conduit system would not be used, and where, in general, the details of construction should be reduced to the simplest form. The limits imposed practically were such as to require that the system should not cost more than a cable road to install. Edison reverted to his ingenious lighting plan of years earlier, and thus settled on a method by which current should be conveyed from the power plant at high potential to motor-generators placed below the ground in close proximity to the rails. These substations would convert the current received at a pressure of, say, one thousand volts to one of twenty volts available between rail and rail, with a corresponding increase in the volume of the current. With the utilization of heavy currents at low voltage it became necessary, of course, to devise apparatus which should be able to pick up with absolute certainty one thousand amperes of current at this pressure through two inches of mud, if necessary. With his wonted activity and fertility Edison set about devising such a contact, and experimented with metal wheels under all conditions of speed and track conditions. It was several months before he could convey one hundred amperes by means of such contacts, but he worked out at last a satisfactory device which was equal to the task. The next point was to secure a joint between contiguous rails such as would permit of the pa.s.sage of several thousand amperes without introducing undue resistance. This was also accomplished.

Objections were naturally made to rails out in the open on the street surface carrying large currents at a potential of twenty volts. It was said that vehicles with iron wheels pa.s.sing over the tracks and spanning the two rails would short-circuit the current, "chew" themselves up, and destroy the dynamos generating the current by choking all that tremendous amount of energy back into them. Edison tackled the objection squarely and short-circuited his track with such a vehicle, but succeeded in getting only about two hundred amperes through the wheels, the low voltage and the insulating properties of the axle-grease being sufficient to account for such a result. An iron bar was also used, polished, and with a man standing on it to insure solid contact; but only one thousand amperes pa.s.sed through it--i.e., the amount required by a single car, and, of course, much less than the capacity of the generators able to operate a system of several hundred cars.

Further interesting experiments showed that the expected large leakage of current from the rails in wet weather did not materialize. Edison found that under the worst conditions with a wet and salted track, at a potential difference of twenty volts between the two rails, the extreme loss was only two and one-half horse-power. In this respect the phenomenon followed the same rule as that to which telegraph wires are subject--namely, that the loss of insulation is greater in damp, murky weather when the insulators are covered with wet dust than during heavy rains when the insulators are thoroughly washed by the action of the water. In like manner a heavy rain-storm cleaned the tracks from the acc.u.mulations due chiefly to the droppings of the horses, which otherwise served largely to increase the conductivity. Of course, in dry weather the loss of current was practically nothing, and, under ordinary conditions, Edison held, his system was in respect to leakage and the problems of electrolytic attack of the current on adjacent pipes, etc., as fully insulated as the standard trolley network of the day. The cost of his system Mr. Edison placed at from $30,000 to $100,000 per mile of double track, in accordance with local conditions, and in this respect comparing very favorably with the cable systems then so much in favor for heavy traffic. All the arguments that could be urged in support of this ingenious system are tenable and logical at the present moment; but the trolley had its way except on a few lines where the conduit-and-shoe method was adopted; and in the intervening years the volume of traffic created and handled by electricity in centres of dense population has brought into existence the modern subway.

But down to the moment of the preparation of this biography, Edison has retained an active interest in transportation problems, and his latest work has been that of reviving the use of the storage battery for street-car purposes. At one time there were a number of storage-battery lines and cars in operation in such cities as Washington, New York, Chicago, and Boston; but the costs of operation and maintenance were found to be inordinately high as compared with those of the direct-supply methods, and the battery cars all disappeared. The need for them under many conditions remained, as, for example, in places in Greater New York where the overhead trolley wires are forbidden as objectionable, and where the ground is too wet or too often submerged to permit of the conduit with the slot. Some of the roads in Greater New York have been anxious to secure such cars, and, as usual, the most resourceful electrical engineer and inventor of his times has made the effort. A special experimental track has been laid at the Orange laboratory, and a car equipped with the Edison storage battery and other devices has been put under severe and extended trial there and in New York.

Menlo Park, in ruin and decay, affords no traces of the early Edison electric-railway work, but the crude little locomotive built by Charles T. Hughes was rescued from destruction, and has become the property of the Pratt Inst.i.tute, of Brooklyn, to whose thousands of technical students it is a constant example and incentive. It was loaned in 1904 to the a.s.sociation of Edison Illuminating Companies, and by it exhibited as part of the historical Edison collection at the St. Louis Exposition.

CHAPTER XIX

MAGNETIC ORE MILLING WORK

DURING the Hudson-Fulton celebration of October, 1909, Burgomaster Van Leeuwen, of Amsterdam, member of the delegation sent officially from Holland to escort the Half Moon and partic.i.p.ate in the functions of the anniversary, paid a visit to the Edison laboratory at Orange to see the inventor, who may be regarded as pre-eminent among those of Dutch descent in this country. Found, as usual, hard at work--this time on his cement house, of which he showed the iron molds--Edison took occasion to remark that if he had achieved anything worth while, it was due to the obstinacy and pertinacity he had inherited from his forefathers.

To which it may be added that not less equally have the nature of inheritance and the quality of atavism been exhibited in his extraordinary predilection for the miller's art. While those Batavian ancestors on the low sh.o.r.es of the Zuyder Zee devoted their energies to grinding grain, he has been not less a.s.siduous than they in reducing the rocks of the earth itself to flour.

Although this phase of Mr. Edison's diverse activities is not as generally known to the world as many others of a more popular character, the milling of low-grade auriferous ores and the magnetic separation of iron ores have been subjects of engrossing interest and study to him for many years. Indeed, his comparatively unknown enterprise of separating magnetically and putting into commercial form low-grade iron ore, as carried on at Edison, New Jersey, proved to be the most colossal experiment that he has ever made.

If a person qualified to judge were asked to answer categorically as to whether or not that enterprise was a failure, he could truthfully answer both yes and no. Yes, in that circ.u.mstances over which Mr. Edison had no control compelled the shutting down of the plant at the very moment of success; and no, in that the mechanically successful and commercially practical results obtained, after the exercise of stupendous efforts and the expenditure of a fortune, are so conclusive that they must inevitably be the reliance of many future iron-masters. In other words, Mr. Edison was at least a quarter of a century ahead of the times in the work now to be considered.

Before proceeding to a specific description of this remarkable enterprise, however, let us glance at an early experiment in separating magnetic iron sands on the Atlantic sea-sh.o.r.e: "Some years ago I heard one day that down at Quogue, Long Island, there were immense deposits of black magnetic sand. This would be very valuable if the iron could be separated from the sand. So I went down to Quogue with one of my a.s.sistants and saw there for miles large beds of black sand on the beach in layers from one to six inches thick--hundreds of thousands of tons.

My first thought was that it would be a very easy matter to concentrate this, and I found I could sell the stuff at a good price. I put up a small plant, but just as I got it started a tremendous storm came up, and every bit of that black sand went out to sea. During the twenty-eight years that have intervened it has never come back." This incident was really the prelude to the development set forth in this chapter.

In the early eighties Edison became familiar with the fact that the Eastern steel trade 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 compet.i.tion 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 transportation 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 a.s.sociated 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 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 circ.u.mstances, 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 ma.s.ses 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 (magnet.i.te) 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 part.i.tion placed below. The non-magnetic gangue descends in a straight line to the other side of the part.i.tion. Thus a complete separation is effected.

Simple though the principle appears, it was in its application to vast ma.s.ses 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 pa.s.sed 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 throughout the various ramifications of the plant, but the princ.i.p.al ones are worthy of mention, such as:

The giant rolls (for crushing).

Intermediate rolls.

Three-high rolls.

Giant cranes (215 feet long span).

Vertical dryer.

Belt conveyors.

Air separation.

Mechanical separation of phosphorus.