ae 
CALORIMETER. 
and are absorbed. In the latter case, the tem- 
perature of the receiving substance is increased ; 
in the former, it is unchanged. The nature of 
the surface of a body has been found to influence 
powerfully both the radiation and absorption of 
caloric. The energy of calorific emanation from 
a cubical tin vessel, coated with different sub- 
stances, and containing warm water (as deter- 
mined by the differential thermometer of Leslie), 
gave, with a covering of 
Lampblack, 100 
Isinglass, 75 
Tarnished lead, 45 
Polished iron, 15 
Tin-plate, gold, silver, ot or copper, “6 1 
Similar results were obtained simply by noting 
| the rates of cooling in vessels of similar shapes 
and capacities with various surfaces. Useful 
lessons have been derived from these discoveries. 
Tea and coffee pots, which are intended to retain 
their heat, are made of bright and polished me- 
tals; and steam-pipes, intended to convey heat 
to distant apartments, are kept bright in their 
course, but darkened where they reach their des- 
tination. The power of different surfaces to ab- 
sorb caloric was found, by coating one of the 
bulbs of the differential thermometer successively 
with different substances, and presenting it to an 
uniformly heated substance, to follow the same 
order as the radiating or projecting quality. 
With regard to combined caloric, it has been 
shown that solids, during liquefaction, imbibe a 
quantity of caloric, which ceases to be obvious, 
both to our senses and to the thermometer. The 
same is also true of solids and liquids in their 
conversion into vapours or gases; a portion of 
caloric, which is essential to the elasticity of the 
| new product, ceases to become apparent. When- 
ever this effect takes place, cold is said to be pro- 
duced ; by which we are only to understand the 
passage of caloric from a free to a latent form. 
The reverse of these phenomena has also been 
satisfactorily established; viz., when the density 
of bodies is increased, either by chemical or me- 
| chanical means, caloric is evolved. For example, 
a high temperature is produced by mingling cold 
sulphuric acid and water; metals become in- 
tensely heated by the augmentation of their den- 
sity through hammering; liquids, by becoming 
solids, or gases by conversion into liquids, also 
evolve caloric. A pound of water, condensed 
from steam, will render 100 pounds of water 50° 
warmer by 11°; whereas, a pound of boiling 
water will produce the same rise of temperature 
in no more than about 13°12 pounds; and, since 
steam and boiling water affect the thermometer 
in the same manner, this effect can be produced 
only from the existence of a much greater quan- 
tity of caloric in the former than in the latter. 
The sources of caloric are six; viz., the sun’s 
rays, combustion, percussion, friction, the mix- 
ture of different substances, and electricity. 
CALORIMETER. An instrument to measure 
| tain from Persia in 1714. 
‘CALOTROPIS.. 655 
the capacity of a body for caloric, or its specific 
caloric. The thermometer measures merely the 
variations of temperature, or sensible heat. The 
body in the calorimeter is placed in the imner- 
most of three concentric vessels, the two outer 
ones containing ice; the quantity of water pro- 
duced by the cooling of the body a given number | 
of degrees, determines its specific caloric. This 
instrument was invented by Lavoisier and La- 
place. In the calorimeter invented by Rumford, 
water is used; the capacity of the body is deter- 
mined by the number of degrees which the tem- 
perature of the water is raised, in cooling the 
body a given number of degrees. 
CALOSTEMMA. A genus of very beautiful, 
tuberous-rooted, Australian plants, of the ama- 
ryllis tribe. The yellow-flowered and the purple- 
flowered species were introduced in 1819, and 
the white-flowered species in 1824; and the last 
is a plant of great elegance, blooming from Feb- 
ruary till March. Another species, called Cun- 
ningham’s, has been more recently introduced. 
All are treated in the same manner as other am- 
aryllideee. 
CALOTHAMNUS. A genus of ornamental, 
evergreen, Australian shrubs, of the myrtle tribe. 
Three species, CO. guadrifida, C. gracilis, and C. vil- 
Josa, were introduced in 1803; and one, C. cla- 
vata, in 1824; and all these have a height of 
about a yard, carry scarlet flowers from July till 
September, and are easily propagated from cut- 
tings. The name calothamnus signifies “a beau- 
tiful rod,” and alludes to the superb appearance 
of the branches, when covered with the scarlet | 
flowers. 
CALOTROPIS. A genus of ornamental, ever- | 
green tropical shrubs, of the swallow-wort tribe. 
The giant species, Calotropis gigantea—called by 
some botanists Asclepias gigantea—is a native of 
the East Indies, and was introduced to Britain 
before the close of the seventeenth century. It 
grows to the height of about six feet, and pro- 
duces white and purple flowers from July till 
September. Its flowers have a handsomely curved 
or contorted form, and give the name calotropis, 
which signifies “beautifully twisted,” to the 
whole genus. Its bark has a somewhat pungent 
property ; and when powdered, and mixed with 
margosa oil, is used in India as an external ap- 
plication for rheumatism. Its root is pale-col- 
oured, bitter, and somewhat pungent; and is 
administered in decoction, by the practitioners 
of India, as a gentle stimulant in cases of fever 
and dyspepsia. The milky juice is used by the 
Tamul practitioners as a cathartic. The whole 
plant is said to be poisonous to sheep and goats; 
and, with its light-coloured, downy, succulent 
leaves, is used in Mysore for tanning leather. 
The powdered flowers are sometimes employed 
by the native Hindoos to adulterate safflower.— 
The tall species grows to about the same height 
as the giant species; and was introduced to Bri- 
~ - Se eee 
