84 Climate and Diversions in 
ball. One of these balls should contain a little* watery 
and the remaining cavity should be as perfect a vacuum ag 
can readily be obtained, The mode of effecting this is well 
known to those who are accustomed to blow glass. One 
of the balls is made to terminate in a capillary tube; and 
when water admitted into the other has been boiled over a 
Jamp for a considerable time, till all the air is expelled, the 
capillary extremity, through which the steam is still issuing 
with violence, is held in the flame of the lamp tll the force 
of the vapour is so far reduced, that the heat of the flame 
has power to seal it hermetically. 
When an instrument of this description has been suc- 
cessfully exhausted, if the ball that is empty be immersed 
in a freezing mixture of salt and snow, the water in the 
other ball, though at the distance of two or three feet, will 
be frozen solid in the course of a very few minutes. The 
vapour contained in the empty ball is condensed by the 
common operation of cold, and the vacuum produced by 
this condensation gives opportunity for a fresh quantity to 
arise from the opposite ball, with proportional reduction of 
its temperature. Y ; £4 
According to a theory that does not admit of positive 
cold, we should represent the heat of the warmer ball to be 
the agent in this experiment, generating steam as long as 
there remains any excess of heat to be conveyed. But if 
we would express the cause of its abstraction, we must say 
that the cold mixture is the agent, and may observe, in this 
instance, that its power of freezing is transferred to a di- 
stance, by what may be called the negative operation of 
steam. 
The instrument, by which this is effected, may aptly be 
called a Cryophorus, which correctly expresses its office of 
frost-bearer. 
XLVIII. Climate and Diversions in the Northern Paris of 
British India. Extracted from a Leiter from an Officer 
an the Army f. 
ee 
W: fone of His Majesty’s regiments of infantry] ar- 
rived at Meerut in the middle of November. You can have 
no conception how cold the weather is at this place. This 
is the cold season; and I can assure you it Is piercingly se. 
* If the ball be more than half full, it will be liable to burst by the ex- 
pansion of water in freezing. 
+ Communicated by Dr. W. Thomson, Kensington, 
A few 
