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clofely examined, it will be found to contain parti- 

 cles of the metal feparated by abrafion, vifible to 

 the naked eye, and further diftinguilhable by expe- 

 riments with the volatile alkali.* Bell-metal con- 

 tains a confiderable portion of copper, therefore 

 thefe mortars are not only liable to abrafion, but 

 corrofion, by all the fubftances that are capable of 

 a6ling upon copper. 



Hence various abforbent, faline, and faponaceous 

 bodies, whether reduced into the form of powders 

 or pills in thefe mortars, may eafily acquire an ac- 

 cidental impregnation of copper, 



Brafs mortars and utenfils are equally fubjed to 

 the fame inconvenience. 



Brafs and copper fcales fpeedily contrad verdi- 

 gris, from fait and groceries being weighed in them, 

 as appears from the green efflorefcence with which 

 we generally fee them difcoloured. 



Copper Roofs. 



Of late the Britifh copper mines have poured 

 forth the ore in fuch abundance, that this metal 

 begins to ufurp the place of lead, and to extend its 



• See Experiments and Obfervations on Copper and Bell-metal, 

 1786. 



dominion 



