The Antiquities of Orissa v1.c8.57.2

v1.c8.57.2

others, again, are evidently ferruginous pebbles of decomposed gneiss, or of sandstone, if the rock prevail in the neighbourhood. These little nodules are frequently scattered over the country by the denudation and distintegration of the deposit containing them. In places the substance is so soft that it may be cut, though with difficulty, with a spade; in other places it hardens into a firm rock, sometimes cohering only in the form of large blocks, the intermediate portion remaining loose and gravelly, but frequently forming a hard mass, which covers the surface for considerable areas. It is only at the surface that the rock becomes thoroughly hardened; the lower portion requires exposure to give it firmness and strength: when exposed it becomes cavernous, owing to the washing away of the softer portions, and apparently a chemical change takes place, whereby the iron becomes altered from the state of anhydrous peroxide (and perhaps also of magnetic oxide) into that of brown or hydrated peroxide. To this chemical change the coherence may perhaps partly be attributed; much, however, is doubtless due to the more thorough drying of clay by the heat of the sun."17 Dr. Oldham, commenting on the value of the laterite as a building material, observes: "Few rocks present greater advantages from its peculiar character; it is easy to cut and shape when first dug, and it becomes hard and tough after exposure to the air; while it seems to be very little acted on by the weather.