found in the Neighbourhood of Glasgow. 403 



Sulphate of lead ... 74*8, or 1 atom. 

 Oxide of copper ... 19*7, or 1 atom. 

 Water 5-5, or 1| atom. 



100*0 



It is therefore a compound of-one atom of sulphate of lead 

 and one atom of hydrate of copper. The blue colour shows 

 that the oxide of copper which it contains is combined with 

 water. 



4. Sulphato-carbonate of lead. This species has been 

 hitherto observed only at Lead Hills, at least so far as I know ; 

 the colour is yellowish or greenish white; it is usually crystal- 

 lized in oblique four-sided prisms. Mr. Brooke analysed it 

 and described it in 1820. By the kindness of Mr. Brown, 

 I got a sufficient quantity of it to subject it to analysis. I found 

 the specific gravity to be 6'3197j which is rather less than 

 that given by Mr. Brooke. My analysis agrees very nearly 

 indeed with that of Brooke. I obtained 



Carbonate of lead 46'04 

 Sulphate of lead . . . 53-96 



100-00 



showing that it is a compound of one atom of carbonate and 

 one atom of sulphate of lead combined together. 



5. Sulphato-tricarbonate of lead. This species is also pe- 

 culiar to Lead Hills. It was first noticed by Bournon. Mr. 

 Brooke described and analysed it in 1820. By the kindness 

 of Mr. Brown, I was enabled to subject it to analysis a few 

 months ago. The lustre is splendent, and the colour yellowish- 

 white. It occurs crystallized both in rhomboids and prisms. 

 I found its specific gravity exactly 6*000. Its constituents 

 were 



Carbonate of lead 72-57, or 3 atoms. 

 Sulphate of lead 27'43, or 1 atom. 



100-00 



This almost coincides with the previous analyses of Brooke 

 and of Stromeyer, who also subjected this mineral to analysis. 



6. Phosphate of lead. This species occurs in Lead Hills 

 and Wanlock Head in considerable quantity, and exhibits a 

 variety of colours, chiefly green, yellow and brown. It is 

 frequently crystallized in six-sided prisms,but more commonly 

 in these mines in cauliflower-like vegetations. 



It is curious that phosphate of lead has never yet been 

 found native except mixed with chloride of lead. The pro- 

 portions vary somewhat ; but the average may be stated one 



2D2 



