Fig. 50. Operating mechanism for stock-line recorder.

The amount of information obtainable as to the way the furnace is settling, whether steadily or by slips, is quite remarkable. One accustomed to the type of chart produced by a given furnace can tell by a glance at it whether the furnace is working normally or not, while the check on the fillers, on the human side, is an absolute one since it must work if the furnace is filled, and in a number of years' experience no method was ever found by which the machine could successfully be "beaten".

Fig. 60. Chart of stock-line recorder.

The subject of distribution is so vast, the number of variables and their reactions upon one another being practically infinite, and our knowledge of what the furnace really requires is so exceedingly limited, that the little we know on the subject has only been developed by an utterly disproportionate amount of trial and experimentation, both with models and with furnaces, and by the slow process of elimination of the most unfit. It is probable that a book could be written upon the subject if one were willing to go back and compile the results of the experience of furnacemen of the older generations.

But the question whether we will or will not use mechanical filling for furnaces has been settled for us, as have so many other questions, not upon the technical ground of whether its distribution is better than that of the hand-filled furnace, or the technical results better or worse than that of its predecessor, but by the stern law of necessity. The waning supply of men available for continuous heavy work, and the increasing wages which they command, combined with the absolute necessity of continuous operation irrespective of all other considerations, have forced us to adopt mechanical filling. There is no reason to believe that circumstances will ever alter so that large plants will be able to go back to hand-filling, even if they should so desire.

It remains, therefore, only for us to use our best endeavors to find out the fundamental laws of distribution, and then to design an apparatus which will conform with those laws and survive under the conditions on the top of the furnace. These are that any apparatus placed there shall receive a scant inspection surely not oftener than once a shift; that a shut down for its repair or for overhauling will be tolerated certainly not oftener than once in six months; that it must operate twenty-four hours a day, and seven days a week; that it must practically always be almost at the limit of working temperature for ordinary machinery; that it must be not infrequently exposed to a much higher temperature and often to flame itself, and that it must work in an atmosphere composed largely of the dust of one of the most abrasive materials in the world. That, further, it shall receive its material with irregularities depending upon a thousand circumstances, and shall smooth these out and deliver the material properly to its place on the main bell. That it shall pass pieces of scrap iron up to several hundred pounds in weight, two or three feet in length, and of almost inconceivable roughness, without injury to itself, and without delay, and that finally the total height through which the material must pass in the performance of these operations shall be a minimum, so that the coke shall be broken up as little as possible.

If in the scant twenty years which have elapsed since the mechanical top became widely introduced we have not achieved perfection in all these results, it is perhaps nothing to cause surprise. In contemplating the long distance we have come from the vast amount of expensive labor, the derangements of the furnace due to frequent inability to keep it full and from the horrible results of the early attempts at mechanical filling, I think we have every reason to feel, if not satisfied, at least that we have made great headway, in one of the most difficult tasks of designing ever submitted to the engineer and metallurgist.