at the works of Piepenstock & Co., belonging to the Hörder Society, in 1848. It found its way to America about twelve years later; but it has not received the attention from American engineers

Fig. 48.—Universal Mill. that the value of its constructive ideas justifies. The first iron beams for use in buildings rolled in America were made the mill of Messrs. Cooper & Hewitt, at Trenton, N. J., in the spring of 1854. They were seven inches deep, weighing about eighty-one pounds per yard. They were used in the construction of the Cooper Institute and the building of Harper & Brothers, and also by the Camden and Amboy Railroad for rails. A special "train of rolls," the invention of William Burrows, was constructed for doing this work. An elevation of the "finishing rolls" of this "train" is given in Fig. 49. It will be seen that there are three short rolls, AAA, whose axes are vertical and supported by a cast-iron frame or housing, D I). Besides these vertical rolls there are two horizontal rolls, E E. The power was transmitted to the mill from the main driving-shaft B, through the bevel gearing B¹, B², the three spur-gears B⁵, and the spindles B⁸. This was the only mill of its kind ever erected, and after a few years it gave place to a "three-high train" which is the kind of mill exclusively used in America at the present time for the manufacture of the various forms of "beams," etc., known as "structural shapes."

The space available will not permit of a detailed description of the various improvements in machinery and methods that have been brought forward within the last thirty years, and we can only briefly mention the more prominent.

In 1859 John and George Fritz (par nobile fratrum)^[1] patented