354 J. Lawrence Smith on Emery. 
My frequent ‘daily examinations of the furnaces in operation 
made me familiar with the condition in which the contents were 
at differeut times, and considering the facts before stated, I ac- 
count for the production of the crystals in the. following way. 
When the furnace, newly constructed or lined with fire- brick, 
is fired and. charged with alkali and chrome: ore, much of the 
fused chromate of potash formed, is absorbed by the porous bricks, 
and I-observed that it had penetrated througts three or four 
courses of bricks and mortar 
_ After the-furnace has been long i in operation the bricks become 
saturated, and vitrified, to a certain depth; and the floor and 
sides of the furnace become incrusted with a vitreous. coating, 
which is constantly increasing. The parts more remote from the 
_ fire are consequently better protected from changes and variations 
- of temperature, and are exempt from the inne of: more fused 
material. 
The chromate of potash i is thus kept for a ae time at a uni- 
form high-temperature, and gradually losing its potash from vola- 
~~ tilization, the chromic¢-acid (Gr) in combiriation with it loses ony 
“Se es — saat (#) and eeynaiiiaes. 
Cae Penn 
Art. XXXV.—Memoir on Emery; by J. Lawrence Smrrs, 
M.D.—F'rst part—On the Geology — beepers of. Emery, 
— from. observati tons made in Asia "Mino 4 
Read before ihe. “heademny” of. Sciences of the Fre ench Institute, Jay 15th, 1850, 
and commiunicat ted by the author for this Journal. 
Or all the mineral substances employed i in the arts, ie have 
offered so little opportunity for. geological examination as emery, 
aad ee our knowledge of it in this er is very 
imit 
