Edison Makes Portland Cement

Long before Edison ever thought of going into the manufacture of cement he had very pronounced opinions of its value for building purposes. More than twenty-five years ago, during a discussion on ancient buildings, he remarked: "Wood will rot, stone will chip and crumble, bricks disintegrate, but a cement and iron structure is apparently indestructible. Look at some of the old Roman baths. They are as solid as when they were built."

With such convictions, and the vast fund of practical knowledge and experience he had gained at Edison in the crushing and handling of enormous masses of finely divided material, it is not surprising that he should have decided to engage in the manufacture of cement.

He was fully aware of the fact that he was proposing to "butt into" an old-established industry, in which the principal manufacturers were concerns which had been in business for a long time. He knew there were great problems to be solved, both in manufacturing and selling the cement. These difficulties, however, only made the proposition more inviting to him.

Edison followed his usual course of reading up all the literature on the subject that he could find, and seeking information from all quarters. After thorough study he came to the conclusion that with his improved methods of handling finely crushed material, and with some new inventions and processes he had in mind, he could go into the cement business and succeed in making a finer quality of product. As we shall see later, he "made good "

This study of the cement proposition took place during the first few months of his experimenting on a new storage battery. In the mean time Mr. Mallory had been busy arranging for the formation of a company with the necessary money to commence and carry on the business. One day he went to the laboratory and told Mr. Edison that everything was ready and that it was now time to engage engineers to lay out the works.

To this Edison replied that he intended to do that himself, and invited Mr. Mallory to go with him to one of the draughting-rooms upstairs. Here Edison placed a sheet of paper on a draughting-table and immediately began to draw out a plan of the proposed works. He continued all day and away into the evening, when he finished; thus completing within twenty-four hours the full lay-out of the entire plant as it was subsequently installed. If the plant were to be rebuilt to-day no vital change would be necessary.

It will be granted that this was a remarkable engineering feat, for Edison was then a new-comer in the cement business. But in that one day's planning everything was considered and provided for, including crushing, mixing, weighing, grinding, drying, screening, sizing, burning, packing, storing, and other processes.

From one end to the other the cement plant is about half a mile long, and through the various buildings there passes, automatically, each day a vast quantity of material under treatment. In practice this results in the production of more than two and a quarter million pounds of finished cement every twenty-four hours.

Not only was all this provided for in that one day's designing, but also smaller details, such, for instance, as the carrying of all steam, water and air pipes and electrical conductors in a large subway extending from one end of the plant to the other; also a system by which the ten thousand bearings in the plant are oiled automatically, requiring the services of only two men for the entire work.

Following this general outline plan of the whole plant by Edison himself there came the preparation of the detail plans by his engineers. As the manufacture of cement also involves the breaking and grinding of rocks, the scheme, of course, included using the giant rolls and other crushing, drying, and screening machinery invented by him for the iron-concentrating work, as mentioned in our last chapter.

No magnetic separator is necessary in cement-making, but there were other processes to provide for that did not occur in concentrating iron ore. One of them relates to burning the material, which is one of the most important processes in manufacturing cement.

Perhaps it may be well to state for the information of the reader that in cement-making, generally speaking, cement-rock and limestone in the rough are mixed together and ground to a fine powder. This powder is "burned" in a kiln and comes out in the form of balls, called "clinker." This again is crushed to a fine powder, which is the cement of commerce.

It will be seen, therefore, that the quantity of finished cement produced depends largely upon the capacity of the kilns. When Edison first thought of going into cement-making he expected to use the old style of kilns, which were about sixty feet long and six feet in diameter, and had a capacity of turning out about two hundred barrels of clinker every twenty-four hours. He is never satisfied, however, to take the experience of others as final, and thought he could improve on what had been done before. He discussed the project with Mr. Mallory, who says:

"After having gone over this matter several times, Mr. Edison said, 'I believe I can make a kiln which will give an output of one thousand barrels in twenty-four hours.' Although I had then been closely associated with him for ten years and was accustomed to see him accomplish great things, I could not help feeling the improbability of his being able to jump into an old-established industry—as a novice—and start by improving the 'heart' of the production so as to increase its capacity four hundred percent But Mr. Edison went to work immediately and very soon completed the design of a new type of kiln which was to be one hundred and fifty feet long and nine feet in diameter, made up in ten-foot sections of cast iron bolted together and arranged to be revolved on fifteen bearings. He had a wooden model made, and studied it very carefully through a series of experiments. These resulted so satisfactorily that this form was finally decided upon, and ultimately installed as part of the plant.

"Well, for a year or so the kiln problem was a nightmare to me. We could only obtain four hundred barrels at first, but gradually crept up through a series of heart-breaking trials until we got over eleven hundred barrels a day. Mr. Edison never lost his confidence throughout the trials, but on receiving a disappointing report would order us to try it again."

Although the older cement manufacturers predicted utter failure, they have since recognized the success of Edison's long kiln, and it is now being used quite generally in the trade.

Another invention of minor nature but worthy of note relates to the weighing of the proportions of cement-rock and limestone. In most cases the measurement is usually by barrow loads, but Edison determined that it must be done accurately to the pound, and devised a means of doing it automatically, for, as he remarked, "The man at the scales might get to thinking of the other fellow's best girl, so fifty or a hundred pounds of rock, more or less, wouldn't make much difference to him."

With Edison's device the scales are set at certain weights and the materials are fed from hoppers. The moment the scale-beam tips an electrical connection automatically stops the feed and no more can be put on the scale until the load is withdrawn.

Another and important new feature introduced by Edison was in raising the standard of fine grinding of cement ten points above the regular standard of seventy-five percent through a two-hundred-mesh screen. By reason of the great improvements he had made in grinding machinery he could grind cement so that eighty-five percent passed through a two-hundred-mesh screen. As cement is valuable in proportion to its fineness, it will be seen that he has thus made an advance of great importance to the trade.

We cannot enter into all the details of the numerous inventions and improvements that Edison has introduced into his cement plant during the last eight or nine years. It is sufficient to say that by his persistent and energetic labors during that period he has raised his plant from the position of a new-comer to the rank of the fifth largest producer of cement in this country.

A remarkable instance of the power of Edison's memory may be related here. Some years ago, when the cement plant was nearly finished and getting ready to start, he went up to look it over and see what needed to be done.

On the arrival of the train at ten-forty in the morning he went to the mill, and, starting at one end, went through the plant to the other end, examining every detail. He made no notes or memoranda, but the examination required all day.

In the afternoon, at five-thirty, he took a train for home, and on arriving there a few hours later got out some notebooks and began to write from memory the things needing change or attention. He continued on this work all night and right along until the next afternoon, when he completed a list of nearly six hundred items. This memory "stunt" was the more remarkable because many of the items included all the figures of new dimensions he had decided upon for some of the machinery in the plant.

Each item was numbered consecutively, and the list copied and sent up to the superintendent, who was instructed to make the changes and report by number as they were done. These changes were made and their value was proven by later experience. Edison's achievements have made a deep impression on the cement industry, but it is likely that it will become still deeper when his "Poured Cement House" is exploited.

A few years ago he conceived the idea of pouring a complete concrete house in a few hours. He made a long series of experiments for producing a free-flowing combination of the necessary materials, and at length found one that satisfied him that his idea was feasible, although experts said it could not be done.

His plan is to provide two sets of iron molds, one inside the other, with an open space between. These molds are made in small pieces and set up by being bolted together. When erected, the concrete mixture is poured, in from the top in a continuous stream until the space between the molds is filled.

The pouring will be done in about six hours, after which the molds will be left in position about four days in order that the concrete may harden. When the molds are removed there will remain standing an entire house, complete from cellar to roof, with walls, floors, stairways, bath and laundry tubs, all in one solid piece. These houses, when built in quantity, will probably cost about twelve hundred dollars each.

Mr. Edison intends this house for the workingman, and in its design has insisted on its being ornamental as well as substantial. As he expressed it: "We will give the working man and his family ornamentation in their house. They deserve it, and besides, it costs no more after the pattern is made to give decorative effects than it would to make everything plain."

The molds for the first type of the Edison poured house are nearly completed, and it is probable that in the near future he may be able to find sufficient time to carry this project into actual practice.