any sediment that may have gathered in the pipe connecting the basin and the sewer.

Inlet Castings. There are many different types of castings

FIG. 44. Brick Catch-Basin. Borough of the Bronx, New York.

which are used as catch-basin covers and inlets. If a casting is so placed that traffic will pass over it, a much stronger type

Vit.Pipe

will be required than when this is not the case. Figs. 46, 47 and 48 show inlets which are used to a considerable extent on park highways and on roads where there are no curbs. Attention

FIG. 45. Brick Catch-Basin. Borough of the Bronx, New York.

is called to the construction as shown by Fig. 47, the casting of which has a raised portion on the back so that if the lower

part becomes clogged the raised part will still take water. Fig. 46 and Fig. 48 show two types of inlets which lay flat and are sufficiently strong to take the traffic. These types are frequently used with great satisfaction in road work, and may be used also within the cities as well, the grating being placed in the gutter next to the curb. Those gratings with longitudinal openings extending the full width of the grate should be placed so that the openings are perpendicular to the line of travel. Covers for catch-basins roughened so that the danger from

and manholes should be slipping will be avoided. This is essential whether the catchbasin is located in the sidewalk or the carriageway. Fig. 49 is a view of the iron casting used in the construction of catch-basins in the Borough of the Bronx, New York City.

Location of Catch-Basins. Catch-basins on roads are lo

cated with the inlet in the gutters or ditches. Since generally no

curb exists, the inlet serves as the only opening to the basin unless a special form of casting is used, as shown in Fig. 47. In cities where the water drains towards a street intersection there are two methods of placing the catch-basins. One method is to place a basin or inlet at each corner. Such a procedure, however, does not allow the construction of an efficient inlet, and, moreover, the inlet coming directly at the corner usually causes the

flooding of street crossings during rain storms. In the other method a basin or inlet is located on both sides of the corner. It is not necessary to construct more than one catch-basin in this case, since one may serve for the two inlets. The inlet to the catch-basin is sometimes only a vertical opening in the curb. Again, some form of casting is used which provides a horizontal well as a vertical opening. Frequently catch-basins

FIG. 49. Inlet Casting. Borough of the Bronx, New York.

are constructed entirely beneath the sidewalk. This method has the objection that in cleaning the basin the sidewalk is obstructed. If the basin is constructed partly under the sidewalk and partly under the gutter with the cover or grate through which the basin is cleaned in the gutter, the above objection is done away with.

CHAPTER VI

FOUNDATIONS

NECESSITY OF FOUNDATIONS. All loads must ultimately be carried by the subsoil. The subsoil, without the construction of some artificial foundation in addition, will not be sufficient under most conditions. All forms of block pavements and sheet asphalt, for instance, cannot be built and maintained successfully on a subsoil foundation alone. It is practically impossible to make every part of a soil foundation the same, and a rigid uniform base is one of the essentials to success in the construction of any of the above pavements, otherwise the surface soon loses its shape, which accelerates the wear. The importance of thorough drainage of the subsoil should be realized, since no matter what form of foundation is contemplated, a poorly drained subsoil will endanger its success.

The conclusions of the Second International Road Congress held in Brussels in 1910, in regard to foundations, are:

"The strength of road foundations should be increased in proportion as the supporting power of the ground decreases. The foundation should have more body and resistance, the more it is exposed to internal deterioration and external wear.

"In the choice of the system of foundation for both stone block pavements and metalled roads, due consideration should be given to the condition of the subsoils, with regard to the possibility of their drainage, to their geological nature, and to the nature of the materials of the locality. In order to determine the thickness and the extent of the foundations, the pressure per unit area should be made compatible with the carrying resistance of the soils, observed under the most unfavorable conditions." CLASSIFICATION. The subject of foundations will be considered under two main heads, namely, natural foundations and artificial foundations. With the exception of earth roads, the