SULPHURIC ACID FOR WATER. 389 
is allowed to pass through them they will commu- 
nicate warmth, or even hotness (if the same should 
upon trial be found to give additional benefit), to 
the whole internal aerial space of the chambers: 
and, it does not seem to be of much consequence 
whether the pipes be laid through the acid on the 
floors, or only through the space immediately 
above that liquid ;* for, in either case, the aerial 
space would become heated. Such a contrivance 
would be of benefit in two ways ;—it would heat 
and supply the aerial space with vapour, and would, 
inevitably, at the same time, be considerably con- 
centrating, instead of diluting, the liquid acid on 
the floors. 
It may be said, that in the foregoing remarks 
I have not taken into consideration that the heat, 
conveyed into the chambers from the furnace 
* Perhaps the greatest advantage would be obtained if the 
pipes were laid both through the liquid and through the space 
above the liquid. 
7 It is advisable, that in erecting chambers attention should 
be given to their form: those having the least cooling surface, 
in relation to their internal capacity, being the most prefer- 
able. If the form of a cube be departed from, it should be 
in the depth: indeed, from what I have said (page 383) re- 
garding the necessity of the quickly depositing of the crys- 
talline substance, it may be inferred that there is chemical 
reason why they should be less deep than cubical, indepen- 
dently of the fact that in such case they will more firmly 
support themselves. 
