Manufacture of Sulphat of Iron. 327 
For three or four years past they have adopted a more 
expeditious method of decomposition, which was discover- 
ed in the first place by accident. They break the ore into 
much smaller fragments, three inches and less in diameter, 
and throw them into a convenient heap, taking care to leave 
air holes at the base, so as to allow the air to pass freely 
through the heap. On applying water the decomposition 
commences, and so much heat is evolved, as presently to 
raise the temperature of the heap to such a degree as to 
charr wood, boil water, sublime sulphur, &c. Great quan- 
tities of sulphurous acid gas are evolved during the process, 
and in the course of three or four weeks the whole becomes 
oe and Ae to fall into Fux state of powder. It 
yoleanoes happened to be burning. The sulphurous acid 
produced had run down the side of the hill below, and kill- 
ed the grass and leaves of the trees for several rods, as com- 
pletely as though they had been scorched by fire. It was 
even dangerous to approach it except on the windward side. 
I thrust a stick into it and it was charred to blackness in a 
the -heap by sublimation. I was informed that ‘the ae 
astally athed and ran down into the cavities, and that it 
frequently burned with flame in various parts of the heap. 
he manufactory in which the processes of evaporation 
and erystalization are performed, is placed on the declivity 
wits below me mine. This gives great facility to all the 
ing the various reservoirs to be so arranged 
one above saikoe that the liquor may be transferred from 
One process to another merely by means of a trough. © 
The bottoms of the evaporating vessels are z ead, 
and about ten feet square; the sides are of wood abou 
three or four feet high. The bottom is sup d bya 
number of parallel brick walls, placed at a small distance 
from each other. The avenues or arches between these 
walls communicate at one end with the arch in which the 
fire is placed, and at the other with the common flue. 
‘The ore is a sulphuret of iron with a small proportion of 
copper; and the solution, first obtained, is is a sulphate of iron 
