TROY WEIGHT. 157 



24 grs. 480 gra. 5760 grs. 



NOTES. 1. A carat is a weight of about 3.2 grains, 

 and is used by jewellers to weigh diamonds. The term 

 carat is also used to denote the fineness of gold. When gold 

 contains 18 parts pure gold and 6 parts alloy, which is usu- 

 ally silver and copper, it is said to be 18 carats fine. Gold 

 14 carats fine contains 14 parts pure gold and 10 parts 

 alloy, &c. 



2. The term Troy is derived from Troyes, where the 

 weight was first introduced into Europe, about the 12th 

 century. 



3. The term pennyweight is derived from the weight of 

 the old silver penny. The term grain is derived from the 

 custom of using the grains of wheat, 24 of which were taken 

 to determine the weight of a pennyweight. 



4. The symbol oz. is derived from the Spanish word onza, 

 an ounce ; Ib. is from the Latin libra, a pound. 



5. The standard unit of weight is the troy pound. It 

 equals the weight of 22. 79 -feu. in. of distilled water at the 

 temperature of 39 S3' F., the barometer being at 30 in. 



