and the Places tuhere found. 437 



uarts. When it is to be employed as teeth -powder, it muft 

 be pounded remarkably fine J and even then it will attack 

 the teeth too ftrongly. 



In countries where pumice ftone can be procured at ^ 

 cheaper rate than a»mono; us, it is pounded and mixed with 

 ttle mortar ufed in building. This is done in Italy * ; and 

 the cafe muft have been the fame in former times, as pieces 

 of it are frequently to be obferved in the mortar of ancient 

 walls. It has this binding property in common with terras, 

 pozzolana, and other volcanic produftions. From this cir- 

 fumftance we might be induced to conje£turc, that the 

 ancients mixed fine terra Jlgtllaris with pumice ftone 

 poarfely pounded, and formed it into moulded mafTes, which 

 they dried in the fun, in order to make thofe bricks for 

 building, which, as Strabo, Pliny, Antigonus Caryftius, Vi- 

 truvius, and others f, tell us, with fome degree of wonder, 

 fvvam in the water ; and that, on account of their lightnefs, 

 they were peculiarly well adapted for many ufeful purpofes. 

 They exprefsly fay, that the ancients ufed, in making them, 

 the mineral employed for cleaning filver-plate, which we mav 

 confider to have been pumice ftone; though many other kinds 

 of earths are fit for the fame purpofe. This conjefture has 

 given rife, in modern times, to experiments which have not 

 yet been attended with cornplcte fuccefs. It will be diifi- 

 cult, indeed, to obtain bricks fo light by mixirig clay witli 

 finely pounded pumice flone, as it will then form a body too 

 compa£l and heavy. From a palfage in. the TraveJs of Peter 

 Delia Valle % oi^^ might be induced to conje6lure, that the 

 art of making fw-imming bricks was known at Ormus, an 

 ifland in the Perfian Gulph, unlefs he meant perhaps to fay. 

 that pumice ftone was employed there for building as ii^ 



• Labat's Reife (lurch Ilalicn, iv. p. 16. 



f Tdc tcdimpnics of the ancients on this fubjciSt I have gi\ en in a 

 note to the Uijloria Mirab. of Antigonus Caryftius, cap. clxxxvii. p. 218. 

 1 D'jila Vallo's Travels. Geneva, j674- fol. 3. p, 235. 



Sicily ; 



