found in the Neighbourhood of Glasgow. 405 



the result approaches pretty near the truth. The specific 

 gravity by my trials was 5'000, but the specimen was not ab- 

 solutely pure. 



From 3*29 grains, I obtained 



Sulphate of lead .... 1'74- 

 Carbonate of lead ... 1 '05 



Oxide of copper . . . 0*44? 3'23. 



The 0*06 gr. wanting to make up the original weight was 

 foreign matter and water. 



According to this analysis 100 parts of the ore would have 

 given Atoms. 



Sulphate of lead... 52'88 1'46 1| 



Carbonate of lead . 31-91 1 1 



Oxide of copper . . 13'37 1'4 \\ 



Impurity and water 1*84 



100 



Mr. Brooke supposes the copper to exist in this mineral 

 in the state of carbonate, but the result of the analysis just 

 stated, is quite inconsistent with that opinion. It would, 

 however, be desirable, in order to be quite certain, to repeat 

 the analysis on a larger quantity of the mineral than I could 

 procure. 



8. Chromo-phosphate of lead. This beautiful mineral ex- 

 ists in the Wanlock Head mine in considerable quantity. It 

 has a beautiful orange colour, without any of the red tinge 

 which characterizes chromate of lead. It is often in cauli- 

 flower concretions; but it occurs also crystallized in six-sided 

 prisms, constituting the common form which characterizes 

 phosphate of lead. I ascertained many years ago that this 

 beautiful orange colour which distinguishes this ore was owing 

 to the presence of about two per cent, of chromate of lead ; the 

 rest was a mixture of subsesquiphosphate of lead and chloride 

 of lead in nearly the same proportions as in the green va- 

 rieties. 



9. Vanadiatc of lead. This very rare ore has hitherto 

 been found only in Mexico and at Lead Hills. It was ana- 

 lysed in 1804 by Del Rio, who announced the existence in 

 it of a new metal. This was contradicted by Collet Des- 

 cotils, who affirmed that what Del. Rio took for a new metal 

 was chromium ; and certainly the resemblance between 

 chromium and vanadium is considerable. 



The specimens in my possession I got several years ago 

 from Mr. Doran, an Irish mineral dealer, who told me that 

 he picked them up in an old neglected lead mine in the county 

 of Wicklow, in Ireland. But there is reason to suspect that 

 he was mistaken. 



