In order to facilitate the hauling of the roller over rough roads and to guard against its upsetting, the framework is provided with wheels adjust able in height in relation to the axis of the cylinder (figs. 21, 22). This provision is unnecessary with rollers of moderate size. To avoid the turn ing of the heavy roller every time it is required to go about in the opposite direction, the frame is sometimes fitted -with a tongue or shaft on both sides; or the frame is made in the form of a ring, with which the tongue lias a swivelling connection, so that the horses can carry the tongue around with them to the opposite side of the roller without being- unharnessed.
In the German practice of road-making, the weight of the roller may vary from two and one-half tons unloaded to ten tons loaded. Gillmore, -who is good authority in American practice, commends for gravel roads a roller weig-hing from one and one-half to two tons for the bottom layers, a six-ton roller for the top layer, and for macadamized roads a twelve-ton roller. The heavy roller constructed for the New York City Department of Parks weighed six and one-half tons and could be loaded to twelve tons. It was of two hollow cylinders of east iron set abreast on a strong, wrought-iron axle, working together a length of 5 feet, with a diameter of 7 feet. The cylinders were set in a timber frame, and in the ends were provided with apertures through which broken stone, gravel, etc., could he introduced, by means of which the agg-regate weight of the machine could be increased to twelve tons.
Steam Road-rollers.—Road-rollers propelled by steam-power have lately been used to some extent, and with satisfactory results. Figure 24 (fi/. 20) exhibits a machine of this class built by Ayeling and much used in England. This machine has two driving-rollers in front, one of which runs loose on its axle to enable the machine to turn short curves. The driving-axle is rotated by chain-gearing from the crank-shaft, and similar gearing is used for connecting the steering-wheel with the two large rollers at the rear. These are journaled in a turn-table, which may be rotated horizontally by the steering-wheel to guide the machine in any direction. The machines are of four sizes, weighing respectively fifteen, twenty, twen ty five, and thirty tons. In the heaviest, shown in the picture, the driving rollers weigh six tons, have a diameter of 7 feet, and are 2y, feet long. They have a clear space betixeen them of about 4y,, feet. At the rear are two heavy rollers, placed close together. These are each feet long, and act as a single roller of 5 feet, passing over that portion of the road which the front rollers leave iintonched. The entire machine is self-contained within the frame, and its movements are readily controlled by the engine driver. Its weight is so distributed that nineteen tons rest upon the front rollers and eleven upon the rear rollers.
the common brooms and wooden scrapers, dust-sweepers like that seen in Figures 25 and 26 (pt. 2o) are employed
for street-sweeping. Figures 27 and 28 show a form of sweeper used upon the macadamized streets of Paris. This consists of a suitable framework or body mounted on wheels and dralyn by horses. It carries at the rear end a cylindrical brush about 4Y2 feet long, haying its axis placed obliquely to the axle of the wagon. As it moves along, therefore, it sweeps the mud from the middle of the street to one side, and a second machine, of the same kind, coming after the first, sweeps the stuff into the glitter. The brush is rotated by means of an endless chain driven by suitable gearing from the axle of the wagon, and by means of a lever may be lowered to the street surface and put in rotation, or thrown out of gear by raising- it up when not required to sweep. One such machine, it is calculated, will do the work of thirteen men, and represents a saying over hand labor of about 5o per cent. The ridges of dirt left by the sweeper are removed in the usual manner with shovels and carts, or the operation may be assisted by the use of mucl-scrapers of the pattern shown in Figure 29.
It may be interesting in this place to take notice of several more elabo rate devices invented and used to some extent for the removal of street dust and mud. Figure 3 (p7. 21), for example, exhibits in section a street sweeping machine in which a cylindrical brush is set in rotation by means of gearing from a spur-wheel on the driving-axle. The driving spur wheels engage pinions turning loosely on the counter-shaft, but clutched thereto in such a manner as to allow of free rotation in one direction. The rotary brushes, which obtain their motion from this shaft through chain gearing, deposit the mud in the dumping-receiver, placed directly in front of them. Another forin of machine is seen in Figure 4. In this, the street dirt is swept into a receiver by means of an endless belt set around with brushes and actuated by gearing from the driving-wheels. In American cities sweepers provided with one or several brushes set obliquely to the drivino--axle and actuated therefrom are in common use for removing- ac cumulations of snow and ice from the tracks of the street-railways. With these the snow is thrown up into ridges on one or both sides of the street.
..9red-sfirink/ers.—To lay the dust in advance of the sweeper, various forms of street-sprinkling devices are used. One of these is shown in Fig ure 3o (fii. 2o). This consists of a line of water-pipe connected with flexi ble hose-sections and provided with a suitable nozzle. The line is mounted on swivelling rollers, so that it is readily portable, and when required for Ilse is connected with the city service-pipes, as seen in the sketch. On the streets and in the parks of American cities there are used, during the warm season, various forms of sprinkling-carts, from which the water is dis charged in a spray, the flow being controlled by a valve operated by the driver; these carts are drawn by horses or mules.