The valuable corals are not found at Zanzibar, but the people sell a thin and white-stemmed madrepore, with brocoli-shaped heads of the liveliest red (Tubipora Musica?). Gypsum abounds at Pemba and other places. Ships bring from Maskat a fine hydraulic mortar called Sáraj, the result of burning shells in small kilns (Tandúr for Tannúr). The material is then stored in bags, pounded, and made into paste when required: it sets to stony consistency like the Pozzolana used by the Romans for under-water buildings. I presume that they mix with this calcaire a certain proportion of sand. The natives do not use shell-lime when chewing betel-nut and leaf: they spoil their teeth with the common stuff. The disadvantage of coralline as building material is that it retains for a long time its ‘quarry-water.’ The Arabs dry it involuntarily, and humour their indolence by expending a dozen years in constructing a house—the home, as at Damascus, being rarely finished during the owner’s life. The remedy is to expel the salts of lime and the animal gelatine by baking the stone, as is practised in the South Sea Islands. Kilns would make good lime at Zanzibar: on the island and coast the people now burn the gypsum and polypidoms in heaps piled upon a circle of billets, and the smoke, which fills half the town, is considered wholesome. Instead of being kept unslaked in sacks, it is wetted with sea-water, which prevents it drying, and it is then heaped up in the moist open air. Moreover, it is mixed with sea-sand, which is washed in fresh water, but its salt ‘sweats out’ for many a long year. Thus the best houses are liable to cuticular eruptions during the wet season: the mortar cracks, and is patched with a leprosy of blue, yellow, and green mould. The flat roofs are protected from the rain with thick coatings of this material, pounded to the desired consistency by rows of slave-women and boys, armed with long flat tamps and rude mallets. During the last 15 years the price of lime at Zanzibar has increased five-fold, $11 being now (1857) paid for a small heap; and, as usual, when Europeans are the purchasers, it rises 50 per cent. SECTION 6. The Industry of Zanzibar. The industry of Zanzibar is closely akin to nil; the same may be said of the coast—both are essentially exporting, and cannot become manufacturing centres, at least as long as the present race endures.