264 Description of Mr. Kemp's Two New Thermometers. 
source of caloric is constantly kept up to the liquid, as from its 
large size it would absorb a great quantity of caloric before it be- 
gan to be affected. 
In using this thermometer, it is necessary to immerse it, always 
to the same depth, in the liquid, so as just to cover the tube CD: 
Another thermometer, which is well adapted for investigations 
of this nature, from its great sensibility, is a modifications of Les- 
lie’s differential thermometer. It consists of two balls, A and B, 
Plate VII. Fig. 2. connected by a tube CDEF, having a very fine 
bore, and bent in the manner seen in the figure. The tube passes 
within, and is continued to the bottom of the ball A, where it is 
terminated in sulphuric acid, a portion of which is to be previously 
put into the ball. ‘The other extremity of the tube terminates in 
the ball B, and is bent up within it, as is seen in the figure, te 
prevent any of the liquid from passing along the tube and flowing 
into the ball B, when the temperature of the ball A is increased. 
The quantity of air at the natural temperature is just sufficient 
to cause the liquid to stand at the point E ; and while the tempe- 
rature of both balls remains the same the liquid continues station- 
ary, whatever that temperature may be. 
f both balls be placed into separate portions of water, and they 
be made to enter into ebullition, the liquid will still remain at the 
point E, provided the ebullition gees on in both vessels with equal 
pia 
If the ball A be placed into a glass vessel, and the ball B inte 
a metallic one, we will have the liquid immediately ascending in 
the stem EF, indicating the increase of temperature which takes 
place in the giass vessel over that of the metallic one. We may 
have, by this construction, the two degrees of Fahrenheit’s seale 
made to extend over a very great range. 
In procf of the great sensibility which thermometers of this con- 
struction possess in indicating minute increments of caloric, I may 
state, that during the ebullition of a liquid, the mercury in the 
stem is in a continual vibration, rising and falling slightly at the 
escane of every bubble into che atmesphere. When ebullition is 
carried on with considerable rapidity, a slight accumulation of ca- 
loric takes place in the liquid, which is immediately indicated by _ 
a rise in the stem of the thermometer. 
When this thermometer is used care must be taken to immerse 
both balls inte the boiling liquid, very gradually, so as to raise the 
temperature to an equal degree, cr they may be placed into cold 
water, and the temperature gradually raised, inch prevents de- 
rangement of the instrument. 
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