other; but in a quiet corner of one of the sheds you will find a boy with a heap of these filings before him, separating the brass from the iron by means of a magnet. Only imagine a boy of fourteen or fifteen doing nothing all day long except raking a magnet through a heap of black and yellow dust, and brushing into a separate heap the iron filings off his magnet! You will also see a series of three iron rollers working on each other, by means of which plate iron can be twisted into any given form; a mighty "punch" which will make a hole an inch in diameter through iron an inch in thickness as easily as though it were clay; and a sharp-cutting instrument that shears through sheets of iron as easily as a pair of scissors through a sheet of paper. Go into another shed, and you will see all these various parts getting their last touches from the hand, and being fitted into each other; and here, also you find two or three men engraving, on circular segments of brass, the names the various engines are to be known by. In another shed the engines are being "erected." Here you see from twenty to thirty in all stages of progress. Perhaps the framework only has been laid; or the boiler, with its many rows of long, circular brass tubes, has just been fastened, and is now receiving its outer clothing of long slips of wood; or the whole is complete, merely wanting to be tried on the many lines of rail in and around the sheds. There are two classes of engines here, whose difference is observable at a glance: some have six wheels, two of which are very large, about six feet in diameter, and the other four much smaller. The two first only are driven by the machinery, the others being merely what are called "bearing wheels." With this description of engine more speed than power is obtained, and hence it is used for passenger trains, where a high velocity is required, and where there is usually little weight, comparatively speaking, to draw. The others have only four wheels, not so large as the two just described, but all driven by the machinery. Such engines I are more remarkable for power than speed, and accordingly they are used for luggage trains. In another shed, "The Hospital," will be found a number of engines laboring under various disorders, sent here to be repaired.