The principal cause of the cheapness of these stone roofs is the very little centering, &c., that is requisite. Fur as the ribs, or primary arches, are very light, centering of the simplest kind does for any one of them, and thus for all suc cessively in either room. But as the centering cannot be removed from any rib till its minter:meting ribs are complete, there is of course required one centering for each room, which, when one series of the primary arches is complete, may be removed with ease for the next, till a eon% enient , number are ready for the superior arching, which of course is very quiekly formed (as before described) without any centering.
The material fittest for this kind of building are the various kinds of sand-stone, including the calcareous sand stone of Cuteh. The laterite, or iron-clay, althtmeh a good material, and the only one hitherto used, is apparently not so roper as the substance generally called free-stone, which is worked with saws, &e., and would be found to answer better than the laterite, which can be shaped only with a pickaxe, and is very heavy.
This iron-clay is found to extend from Bancoate, E. N. E., to, I believe, Ceylon. lying over the trap-rock, even on the highest Ghauts, but is very unequal in thickness and quality ; that of Purnalla and Pawnghur, for instance, being of the softest and most porous kind, and that near Mahabulesher of the best. This stone, when exposed to rain, &c. becomes
very hard, if good ; but if taken from any depth, is so soft as to be easily cut with a knife. It is hence called soap-stone at Belgaum and other Madras stations.
If adopted in Europe, buildings of this kind would be as remarkable for warmth as in this country for coolness. But the pla.u.tering outside would not he advisable on am( Milt of the frost ; tiles, however, or slate, would protect the roof completely.
The principal advantages of these buildings in this coun try are, their coolness, and the little expense incurred in annual and special repairs; indeed, the latter will never be required, if the buildings be properly constructed at first. It is also very evident, that they can never take fire, nor can white ants affect them ; of course they could be built of several stories, the form of the floor-ribs being merely a small segment of a circle (or ellipse) instead of a com pound of two, as in the roof. The upper floor of the jailor's house at llutnaghery is thus built, as also part of another house.
Aram.; Reins of a, the sides or walls which sustain the arch.