PHYSICAL AND LITERARY. 349 



When either a muria of fea-falt, a foi- 

 lution of fait ammoniac, or fpirit of fea 

 ialt, (for thefe three have nearly the fame 

 jeffe(9:s), is put into a folution of filver, it 

 becomes milky, and, as it were, cruddled, 

 .and,at length, awhite powder fublides to the 

 bottom : This powder, being waflied with 

 warm water and dried, is foft and impal- 

 pable ; its weight exceeds that of the fil- 

 yer diffolved by more than one lixth part. 

 This powder comes much fooner to fufion 

 than filver, but does not recover the ap- 

 pearance or properties of that metal; for 

 it looks like a piece of yellowifh glafs, 

 femi opaque and brittle, yet bending or 

 yielding a little, whence it gets the name 

 of hma cornea^ or horny filver ; and it is 

 with great difficulty that it can be redu- 

 ced to true malleable and ductile filver. 



When a plate of copper is put into a 

 folution of filver diluted, the furfaceof the 

 copper is immediately covered, as it were, 

 with a coat of filver ; this becomes gra- 

 dually thicker^ and appears tufted, fpun* 

 gy, and loofe : Upon fliaking the plate, 

 large pieces of this cruft fall off, which 



either 



