OF LEAD. 371 



lour, and translucent, occur in Huel Unity in 

 Cornwall. If any confidence can be put in the 

 analysis of these crystals by the late Mr. Gregor, 

 they are composed of 



1 atom arsenic acid 7*75 



1 atom protoxide of lead 21 



28-75 



But the native arseniate of lead from Johann- 

 Georgenstadt, analyzed by Chenevix and The- 

 nard, was a compound of 



1 atom arsenic acid 7'75 



1 atom protoxide of lead 14 



21-75 



It remains, therefore, to determine whether Mr. 

 Gregor' s results be accurate ; if they be, there 

 are obviously two native species of arseniates of 

 lead namely, the neutral and the sesquiar- 

 seniate. 



9- Chromate of lead. This salt also occurs Chromate, 

 native, crystallized in transparent prisms having 

 a fine orange colour. The salt is anhydrous, 

 and composed of 



1 atom chromic acid 6-5 



1 atom protoxide of lead 14 



20-5 



