CORALLINE. 



251 



mecl 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 Saraj, the 

 result of burning shells in small kilns (Tandiir 

 for Tanniir). 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 



