SULPHURIC ACID FOR WATER. 371 
as it is admitted, in support of the argument of 
the retardation being owing to the wis inertie of 
the particles of air, that the obstruction exerted 
by the atmosphere to vapour escaping from the 
surface of water is overcome in proportion to the 
force of the vapour, and as the force of vapour 
is increased by an increase of temperature, I see 
no reason why vapour should not arise from water 
under atmospheric pressure, at /ow temperatures, 
and in a degree proportionate to the force of va- 
pour at those temperatures. 
I am not aware that other incontrovertible facts 
have been adduced in support of the notion, that 
the weight of the atmosphere is the cause of eva- 
poration going on more tardily in air than in vacuo. 
The fact of water and other liquids boiling, under 
diminished pressure, at temperatures very low in 
comparison with the temperatures at which they 
boil under the usual atmospheric pressure, may, 
by some, be considered sufficient foundation, 
whereon to ground such opinion; but, this alone 
is not indubitable evidence ; indeed, it equally 
supports the opposite notion ; for, the character- 
istic appearance of ebullition being only owing 
to bubbles of vapour, formed at the bottom of 
the containing vessel, rushing through the liquid 
