The clay is dug by a gouge spade, which differs from an ordinary spade in having a curved or semicylindrical blade, as well as a tread on its upper edge, to aid the digger in forcing it into the tough clay. A lump of clay dug by the pitman is termed a spit, and in taking out the material it is customary to dig over the area of the bottom of the pit to the depth of a spade and then begin a new spit. The thickness of any bed of clay, therefore, is always judged in spits.

Where a pit is dug so deep that it is not possible for the workman to throw or lift the lumps to the surface of the ground, a platform may be built in the pit, halfway up its side, or else the clay is loaded into buckets (Pl. VI) and hoisted to the surface by means of a derrick operated by steam-power or horsepower. As soon as a pit is worked out, a new one is begun next to it, but a wall of clay, I to 2 feet thick, is commonly left between the two. When the second pit is done, as much as possible of this wall is removed. A platform of planking is laid on one side of the pit on the ground, and the clay thrown upon this, the different grades being kept separate.

When the clay lies above the ground or road level, there is less trouble with water, and it is not necessary to work the clay in pits, although the general system of working forward in a succession of pit-like excavations or recesses is followed. In such banks, the cart or car is backed against the face of the excavation and the clay thrown into it.

Unless a number of pits are being dug at the same time, the output of any cne deposit or of any one grade is necessarily small, since five or six different kinds are sometimes obtained from one pit. It would also seem that by this method any onegrade of clay might show greater variation than if the excavation were more extended, for the reason that since clay beds are liable to horizontal variation, the material extracted from one pit might be different from that taken from another farther on. Against this we may, of course, argue that the clays from different pits get mixed up on the storage pile.

As these pits are small, and the time required for sinking one, viz., two or three days, is not very great, but little water runs into them, although, in some, much water comes from sand.

Trenton.

near

Digging clay by means of open pits. At the top of the bank, in the background, a workman is driving a wedge into the clay in order to break it off. The clay is hauled to the yard in carts. Hackensack.