On a Phenomenon of St. Michael’s Mount in Cornwall. 429 
edulcorated, dilute nitric acid was put toit. A green solu- 
tion formed without any effervescence. Acetate of barytes 
scarcely rendered this solution turbid ; but nitrate of silver 
produced a copious curd-like precipitate, and iron abun- 
dantly threw down copper from it. The green grains in- 
closed in this native sulphate of potash appear, therefore, 
to he a submuriate of copper, of the same species as that 
of the green sands of Peru and Chili. 
Meriatic acid dissolved the yellow ochraceous powder, 
and prussiate of soda and iron produced Prussian blue. I 
am inclined to believe this yellow powder to be a submu~ 
riate of iron ; but its smal] quantity, and the admixture of 
the submuriate of copper, were impediments to entirely 
satisfactory results. Such a submuniate of iron, though, 
if I mistake not, overlooked by chemists, exists; for the 
precipitate which oxygen occasions in solution of green 
muriate of iron contains marine acid. 
Possibly this yellow powder, and the crystals of speculary 
iron which exist in this Vesuvian salt, have been produced 
by a natural sublimation of muriate of iron, similar to that 
of the experiment of the Duke d’Ayen, recorded by Mac- 
quer*, and which was known long before to Mr. Boyle 
and Dr. Lewis t. 
This Vesuyvian salt, considered in its totality, has pre- 
sented no less than nine distinct species of matters, and a 
More rigorous investigation, than I was willing to bestow 
on it, would probably add to their number. 
July 3, 1813, 
LXXIII. On a Phenomenon of St. Michael’s Mount in 
Cornwall. By J. A. De Luc, Esq. F.R.S. Ge, Se. 
To Mr. Tilloch. 
$ir,—Ln the Number of your Philosophical Journal for 
last August, giving the account of a work entitled ‘ Re- 
marks on the Transition Rocks of Werner, by Thomas 
Allan, F.R.S. Edinb.” you transcribe the following’ pas- 
sage: ‘‘ The importance deservedly attached by Dr. Hutton 
to the phenomena of granite veins gave rise to a variety 
of hypotheses, among those who were inclined to consider 
these rocks as an original deposite, who have accounted for 
their formation in different ways. It was first stated, that 
 ™ Dict, de Chimie, art. Fer. : 26 
+ ACourse of Practical Chemistry, by Wm, Lewis, 1746, page 63, note f- 
) they 
