The soil, earth, and rock, of the country from the banks of the Croton to the city of New York, is of one general character. The line cuts a small section of marble of inferior quality, about two miles below the Croton dam. In running through the State farm at Sing Sing, it passes a few hundred feet (mostly by a tunnel) in a marble of pretty fair quality for building and again at Dobbs' Ferry and at Hastings it lightly cuts a similar ;

rock at the latter place marble has been got out to some extent for market. No more ;

marble was discovered by constructing the aqueduct until it reached Harlem river, where in excavating two of the coffer dams to obtain foundation for the piers, marble rock was found in the bed of the river. This is supposed to be a continuation of the stratum that appears in Harlem valley at the Kingsbridge road, near the Hudson river. With these limited exceptions, the prevailing rock of this district is gneiss, of great variety in quality. In many places it affords excellent building stone for ordinary purposes, and to some extent good blocks of hewn stone have been obtained. A very large proportion, however, of this rock is totally unfit for building purposes. The surface soil is generally a sandy loam, containing a very small proportion of argillaceous earth. Below the surface soil, gravel, sand, boulders, or detached rock, have in most cases been found, and also hard pan to a considerable extent. A large proportion of the open cutting, and nearly the whole tunnel cutting, ha.* been through rock. More than 400,000 cubic yards of rock have been excavated.