1851.] OF THE ROYAL INSTITUTION. 83 
Now this is an evil which can be greatly ameliorated, if it cannot 
indeed, be wholly cured ; but it is by a process that to be effective 
must be general, and, therefore, it must be added, compulsory. The 
process is of familiar application in the ventilation of mines, and 
particularly of coal mines.— An up-cast shaft containing a common 
chimney flue carried up at the back of every house, and connected 
with the house-drains at their highest level would give vent to 
the foul air in the drains, and discharge it into the upper air. — 
The foul air evolved by heat expands, and expanding it rises, 
and rising it would be followed by cold air settling down by the gul- 
ley gratings in the streets, thus constituting their inlets downcast 
shafts, and the sewers and drains themselves channels for the cur- 
rents setting to the up-cast shafts, by which they would be relieved. 
The down draught into the sewers would carry with it much soot 
and fine dust, which would settle upon the liquid current and pass 
off with it, and so remove some of the tangible as well as the in- 
tangible impurities, before referred to, from the air in our streets 
and about our houses. 
Much in this way might be effected by the aid of causes in con- 
stant operation ; but if the up-cast shaft to every house were also a 
fire-flue, or were only aided by the draught of a neighbouring fire, 
the up-current would be sufficient not only to prevent the house 
drains from retaining foul air, but the foul air would be thrown off 
into the upper air with better effect and be dissipated innocuously 
and without offence instead of steaming as it now does from the sewers 
into the air where it cannot be avoided. WW atk. 
Artificial Production of the Ruby, &c. 
M. Exseuman of the Sevre works near Paris being present with 
various specimens of the minerals which he has produced artificially ; 
Mr. Farapay stated the process and results generally to the Members. 
The process consists in employing a solvent, which shall first dissolve 
the mineral or its constituents; and shall further, either upon its 
removal or a diminution of its dissolving powers, permit the mineral 
to aggregate in a crystalline condition. Such solvents are boracice 
acid, borax, phosphate of soda, phosphoric acid &c.:—the one 
chiefly employed by M. Ebelman is boracic acid. By putting 
together certain proportions of alumina and magnesia, with a little 
oxide of chrome or other colouring matter, and fused boracic acid, 
into a fit vessel, and enclosing that in another, so that the whole 
could be exposed to the high heat of a porcelain or other furnace, 
the materials became dissolved in the boracic acid ; and then as the 
heat was continued the boracic acid evaporated, and the fixed 
materials were found combined and crystallized, and presenting true 
specimens of spinel. In this way crystals having the same form, 
