It becomes necessary sometimes to wash dirty sand when clean sand can be secured only at a high cost, while the dirty sand can be easily obtained. If only a small quantity is to be washed, it may be done with a hose. A trough should be built about 8 feet wide and 15 feet long, the bottom having a slope of about 19 inches in its entire length. The side should be about 8 inches high at the lower end, and increase gradually to a height of about 36 inches at the upper end. In the lower end of the trough, should be a gate about 6 inches high, sliding in guides so that it can be easily removed. The sand is placed in the upper end of the trough, and a stream of water is played on it. The sand and water flow down the trough, and the dirt passes over the gate with the overflow water. With a trough of the above dimensions, and a stream of water from a 3/4-inch hose, three cubic yards of sand should be washed in an hour.

Fig. 150. Ideal Concrete Block Machine.

Fig. 150. "Ideal" Concrete Block Machine.

Fig. 151. Group of Blocks Made on Hercules Machines.

Fig. 151. Group of Blocks Made on "Hercules" Machines.

Concrete mixers are often used for washing sand. The sand is dumped into the mixer in the usual manner, and the water is turned on. When the mixer is filled with water so that it overflows at the discharge end, the mixer is started. By revolving the mixer, the water is able to separate the dirt from the sand, and it is carried off by the overflow of water. When the water runs clear, the washing is completed, and the sand is dumped in the usual way.

When large quantities of sand are required to be washed, special machinery for that purpose should be employed.

ST. MARY'S CHURCH, WALKERVILLE, ONT.

ST. MARY'S CHURCH, WALKERVILLE, ONT.

Cram, Goodhue & Ferguson, Architects, Boston and New York.

ST. MARY'S CHURCH, WALKERVILLE, ONT.

ST. MARY'S CHURCH, WALKERVILLE, ONT.

Cram, Goodhue & Ferguson, Architects, Boston and New York.