LITTORAL CONCRETE is a rock found close by the sea-shore of the Bombay coast and western coast of the Peninsula of India, resembling the artificial stone formed by the cementation of sand, gravel, or other coarse material, by lime-water or mortar. It is composed of shells, sand, gravel, and pebbles, and varies in its character with the rocks in the neighbourhood, being micaceous towards Cochin and Tellicherri from the quantity of sand and other nodules from the granite and gneiss; gravelly to the north of Bombay and around it, composed almost entirely of fragments of shells. It is met with only in the regions where rains abound. Along the shores of Sind, .Arabia, and the Red Sea, though the material composing it is abundant in a position similiar to that in which it exists on the Malabar coast, it is nowhere cemented into stone. Even on Bombay Island, indeed, the cementation is far from invariable. In one part of the esplanade there is loose sand on the surface, and concrete beneath. At another, sand or concrete, as the case may be, from the surface throughout to the rock. And in a recent excava tion, concrete was found for the first 20 feet, resting on a bed of fine sand, perfectly loose. It is frequently found to rest—as, for example, at Sewreo and Mahim—on a bed of blue clay filled with kankar and mangrove roots, offering evidence of a depression from the time the mangroves grew at high-water mark, so as to permit the gravel deposit to accumulate. The whole must then
have been raised by a second upheaval to its present level. The principal quarries of these are at Versova, about 20 miles to the north of Bombay, where the shore is sheltered by a vast dyke of basalt formerly submerged. In quarrying it, the sand, which seldom extends more taan a few inches down, is first removed, and the rock is smooth on the surface. A space about 12 feet each way is next divided into slabs one foot square, the grooves between them being cut with a light, flat-pointed, single-bladed pick. These are raised successively by a tool something between an adze and a mattock, a single stroke of which is in general sufficient for the detachment of each from its bed. The blocks thus cut out and raised being thrown aside, the bed is once more smoothed, and the operation resumed till the pit reaches the depth of six or eight feet, when, it being no longer convenient to remove the stones by hand or basket, a new pit is cut. This variety of building material is brought in vast quantities to Bombay, where a large portion of the native houses are built of it. It is not very strong, but with admirable cement, employed with lavish hand, it makes a good and economical wall.—Dr. Buist, LL.D., in Bombay Times.