262 Mr. Bell on the growing power of Russia. 
up a constant intercourse with the Christian princes of Colchis and 
Iberia, and with the Armenians, people always attached to the in- 
-terests of the Byzantine emperors by the ties of a common faith. 
By means of it, the Persians, all-powerful under the auspices of 
the great Nushervan, were always baffled in their attempts to esta- 
blish a footing in Colchis. By means of a fleet, the renowned He- 
raclius was enabled to transport an army to the friendly shores of 
Colchis,—explore his way over the mountains of Armenia,—pene- 
trate into the heart of Persia,—and compel the great king to recall 
his hitherto victorious armies to the defence of his crown, his throne, 
and his capital. 
(To be continued. ) 
ART. IV. Description of Tivo Thermometers adapted to indicate 
minute differences of Temperature in the Boiling Point of La- 
quids tn different vessels. By T. K. Kemp, Esq. Lecturer on 
Chemistry.” 
WHILE engaged in making some experiments on the boiling 
point of various liquids, and also in investigating the cause why 
water and some other liquids enter into ebullition at a lower tem- 
perature in metallic than in glass vessels, I found great difheulty 
in marking with accuracy the slight changes which tock place in 
their temperatures on the intreduction of various foreign substan- 
ces, on account of the smallness of the space: indicating each de- 
gree on the scale of thermometers in common use, in consequence 
of the great variety of temperatures which they are constructed to 
determine by a comparatively short stem. 
This is owing to the smallness of the ball and the equality of 
bore throughout the whole extent cf the stem, which of course is 
absolutely necessary where the instrument is employed to deter- 
mine the various degrees of temperature which exist between the 
freezing and boiling points of liquids. When caloric enters the 
mercury contained in the ball of a thermometer, a certain expan- 
sion takes place in it, by which a quantity equal to that expansion 
is displaced and rises in the stem, which becomes the measure of 
the increase of temperature. The quantity of mercury expelled 
for each degree of Fahrenheit, in balls of the ordinary size, is so 
very small that it will not admit of being subdivided upon the 
scale ; and if we increase the size of the ball so as to cause a great- 
er portion of mercury to pass into the stem for each degree of 
* Mr. Kemp has permitted us to lay before our readers this valuable modifi- 
cation of the mercurial and differential thermometers, prior to the publication of 
a series of experiments, which he has conducted with it, on the boiling point of 
liquids. ED. 
