590 THE POPULAR SCIENCE MONTHLY.
iron. In this figure, a is the foundation sill of the mill. This sill rested upon some heavy frames of timber, which in turn were supported by a pair of bottom sills ; the " stands " or " housings " in which the rolls turned were placed directly on the timber sills, a, and secured by long bolts that passed through the lower sills. At this period, and for some years thereafter, in fact, timber foun- dations for rolling-mills were considered absolutely necessary, in order to impart a certain degree of elasticity to the machinery ; and when we consider the rude way in which all machinery was constructed at that time it is not improbable that some elas- ticity was essential to its operation.
In Fig. 45, at b, are seen the " pinions," which were a strong pair of toothed wheels of the same diameter which served to in- sure an equality of rotation in the top and bottom rolls of the mill. These pinions were connected with the rolls by the spindles e e. The rolls at / could be used to make square bars, or to " rough down " the iron preparatory to passing it through the rolls g, which were intended for flat bars of various widths and thick- nesses. This construction of rolling-mill is what is known as a " two-high train," and is so called from the fact that each pair of "stands" or "housings" contains but two rolls placed one above the other. It is obvious that, as the rolls revolve constantly in one direction, the iron, after passing through one of the grooves, would have to be returned over the " top roll " before it could be passed through the next groove for further reduction in section and extension in length. It is also evident that such a method of working wasted half the time and a large amount of the heat of the metal ; but, notwithstanding these and other quite as serious objections to this form of mill, it continued in use until a very recent period, and it is possible that even now there may be found, in localities uninfluenced by the spirit of progress, some examples of this rotary antiquity still in operation.
Up to the year 1844 the rolling-mills of the United States pro- duced little else than bar iron, hoops, and nail plates ; all the early railroads had been equipped with strap rail (flat bar iron provided with " countersunk " holes at proper intervals, through which passed the spikes by which the " rail " was secured to longitudinal stringers of wood), which could easily be rolled in this country ; or with imported T or H rails. The T rail is of American origin, it having been invented by Robert L. Stevens, President and En- gineer of the Camden and Amboy Railroad. Mr. Stevens had the first of these rails rolled at Dowlais Iron Works, in Wales, and they were laid in the track of the Camden and Amboy Rail- road in 1831-32.
The first heavy railroad iron of America manufactured was made at the Mount Savage Rolling Mill, in Alleghany County,