Sect. Hf Agriculture and Vegetation. 135 



of the fait. In the Indies, from which we 

 have moft of our nitre, they expofe earth 

 of a particular kind, mixed with putrefied 

 vegetables, to the air, and from that extract 

 the nitre. Tourncfort tells us, in his travels, 

 vol. 2. p. 289. "In our converfation in 

 " the caravanfera of Erzeron, we learned 

 " from thofe of the caravan of Wan> a 

 " Turkifh town on the frontiers of Perjia^ 

 " that they carefully lay up in heaps the 

 " dirt of the great roads, which are fre- 

 <c quented by caravans of camels. This 

 " earth they warn, and every year get out 

 " of it about i oo quintals of nitre," 



IN the manufactory of nitre at Paris, 

 where there is much made, they expofe the 

 rubbim of old houfes, mixed with the ames 

 of burnt vegetables, to the influence of the 

 air for fome months, and moiften it often 

 with ftale urine j and from thofe materials 

 extract their nitre. After all the nitre is 

 got out of them, they are as fit as before to 

 form more; and are again thrown on {he 

 K 4 heap, 



