154 Scientific Notices — Mineralogy. [Aug. 



of the phosphorus to the iodine be large, and the latter insuffi- 

 cient to cover the former, the action is accompanied by a mo- 

 mentary flash, which I attribute to the combustion of the unco- 

 vered portion of the phosphorus in the scanty portion of atmo- 

 spheric air in the tube. By varying' the proportions of the two 

 substances, 1 can produce the union with or without the extri- 

 cation of light at pleasure." Letter from Dr. Traill to Prof. 

 Jameson. — (Edin. Phil. Journ.) 



Mineralogy. 



12. New Ore of Lead. 



A native compound of chloride and oxide of lead has been 

 lately analyzed by Berzelius. He found it forming part of a 

 specimen ticketted lead spar, from Mendip, near Churchhill, in 

 Somersetshire, in the collection of lead ores belonging to the 

 Royal Academy of Sciences of Stockholm. The specimen itself 

 consists chiefly of carbonate of lead ; but it contains two portions 

 of a yellower colour than the rest, which attracted in a peculiar 

 manner his attention. On examining them by the blowpipe, one 

 of these proved to be molybdate of lead ; the other, which con- 

 stitutes the mineral in question, afforded decisive indications of 

 the presence of muriatic acid. ' 



The new mineral has a pale straw-yellow colour, is easily 

 frangible, and cleaves with a foliated fracture in two directions. 

 The cleavage planes meet under an angle of between 102° and 

 103°. Before the blowpipe it decrepitates slightly, and is easily 

 melted : the fused globule, when cold, has a deeper yellow 

 colour than the original mineral. On charcoal it is reduced to 

 metallic lead, and at the same time emits fumes of muriatic 

 acid ; also with peroxide of copper, and salt of phosphorus, it 

 imparts to the flame the intense blue colour which characterizes 

 muriatic acid. Dilute nitric acid dissolves it with slight effer- 

 vescence, and if several fragments taken from different parts of 

 the specimen be thrown into the acid at the same moment, the 

 effervescence occasioned by them may be observed to be 

 unequal. 



100 parts of it were found to be composed of 



Oxide of lead 90-13 



Muriatic acid* 6-84 



Carbonic acid . . .'. 1*03 



Water 0-54 



Silica 1 46 



100-00 



* That is, muriatic acid, according to the old theory of its constitution ; not hydro- 

 chloric acidm 



