fome Mineral Subjlances. 1 3 
The Feld fpar I made ufe of was given me by that 
moft excellent chemilt, M. rouelle of Paris, and I think 
he told me it came from Alencon. 
In order to make allum of it, I melted ^ j. of it with 
g j ff. of fixed alkaly of cream of tartar, and let the mix- 
ture run per deliquium. This operation is as tedious and 
as ti'oublefome to perform as the liquor Jilicum made with 
flint, quartz, or cryftal, for it is as liable to froth and boil 
over. No neutral fait was here obtained. The deliquium 
with its dregs were mixed with diftilled vinegar, which 
precipitated the fpar : this precipitate, after edulcoration 
and exficcation, was calcined four different times, with 
frefh parcels each time of oil of vitriol, and afforded 
0 vij. and gr. xvi. of good and regularly cryftallized 
allum; the part which afforded no more allum, when 
wafhed and dried, weighed 5 j. and B ij. 
The Labradore flone (c> is alfo a Feld fpar, though not 
fo hard as the former. The like quantity of this, treated 
as the foregoing, gave no marks of neutral fait; the 
quantity of allum was ^ j. ^ j. and gr. xii. ; and the un- 
(e) This Rone is only found on the Coaft of Labradore, and was brought here 
by the direction of the Rev. Mr. la trobe, remarkable for his piety and zeal 
in propagating the gofpel among the favage Indians. This Hone reflects a 
variety of Hne fhining colours, fuch as blue, green, yellow, &c. I doubt not 
but that feveral other Rones, which reflect various and changeable colours, upon 
trial will be found to be Feld fpars. 
6 
diffolved 
