U A SYSTEM OF 



vitriol is required, inftead of any other liquid, to 

 be mixed with the diamond powder. 



If the petty princes in thofe parts of the 

 Indies where precious ftones are found, have 

 no other power nor riches proportionable to 

 the value of thefe gems ; the reafon of it is as 

 obvious as of the general weaknefs of thole 

 countries where gold and filver abound, viz. be- 

 caufe the inhabitants, placing a'falfe confidence 

 in the high value of their pofleifions, neglecl 

 iifeful manufactures and trades, which by degrees 

 produces a general idlenefs and ignorance thro ? 

 the whole country. 



On the other hand, perhaps fome countries 

 plight fafely improve their revenues by fuch 

 traffic. In Saxony, for example, there might 

 probably be other gems found, befides aqua- 

 marines and topazes •, or even a greater trade 

 carried on with thefe than at prefent, without 

 danger of bad confequences \ efpecially under 

 the direction of a careful and prudent govern- 

 ment. 



The half precious ftones, fo called, or gems of 

 Iefs value, as the opal, the onyx, the chalcedony, 

 the carnelian, and the coloured and uncoloured 

 rock criftals, have been employed for ornaments 

 and ceconomical utenfils, in which the price of 

 the workmanfhip greatly exceeds the intrinfic 

 value of the ftones. The antients ufed to en- 

 grave concave or convex figures on them, which 

 now-a-days are very highly valued, but often 

 with lefs reafon than modern performances of 

 the fame kind. Thefe ftones are worked by 

 means of emery on plates of lead, copper, and tin, 

 or with other inftruments; but the common work, 

 on agates is performed at Oberftein, with grind- 

 ftones, at a very cheap rate. When once fuch a 



manuiac- 



