The rollers on which the hammers ran were hardened and turned on hardened shafts. The hammers themselves had chilled faces, and their surfaces running on the rollers were also chilled. The surfaces of the tool-holders and of the bar on which these rocked were provided with hardened strips to the extent that they came in contact with each other. The cams and rollers and their pins were also hardened. When built this machine was found to require only a single alteration. I had welded the cams onto the shaft, the welds being guaranteed by the smith to be perfectly sound. No appearance of unsoundness could be detected when the shaft was finished, but after running a week or two the cams became loose. This also gave me a useful lesson. I was obliged to send to England for blocks of steel, which were bored, finished and keyed on the shaft in the manner shown, and the working surfaces of the cams were hardened. This required the substitution of new hammers, because the cams could not be threaded through the old ones. The hubs of these cams were 6 inches long, covering the shaft. Our company, being satisfied from its design that the machine when finished would prove a success, rented from Mr. Astor a large lot on the south side of Fourteenth Street, west of Ninth Avenue, extending through to Thirteenth Street, and erected and equipped a building and established a stone-yard, where the machine ran successfully for two seasons, principally employed in facing ashlar, as the flat-faced stones of buildings are termed. It turned out with ease 600 square feet of finished surface per day, which was the work of thirty men, and it never broke a stone, however thin. For facing in the machine the stones were set on bars 2 inches thick and 4 inches high, cast on the surface of sliding tables. These were both longitudinal and cross bars, and were provided with holes ³⁄₄ inch in diameter and about 3 inches apart. There were two tables, each 16 feet in length.