COLUMBIUM. 
or 24 feet high; and the flowers have a dark 
blue colour, and have shorter petals and more 
prominent nectaries than the garden varieties. 
Seeds of the wild plant very seldom sport or vary. 
The garden varieties exceedingly differ from one 
another, not only in the colour and fulness, but 
also in the form, of their flowers. Some, called 
rose columbines, have no visible nectaries, and 
are as double-flowered or many-petalled as the 
larkspur ; and these comprise numerous sub- 
varieties, with respectively blue, red, white, and 
chestnut - coloured flowers, or with exquisite 
variegations of some two of these colours, Others 
have sharp- pointed petals, expanding like the 
rays of a star; others have their petals in an in- 
verted form; others have a horn-like expansion 
| of petals ; and all these comprise subvarieties, dis- 
| the other.” 
tinguishable from one another by their colours or 
by their comparative singleness or fulness. “From 
the different shapes of these flowers,’ remarks 
Miller, “ any person not well skilled in the cul- 
ture of plants would suppose they were distinct 
from the others; but having several years sown 
their seeds, which were collected with great care, 
I have found them always varying from one to 
Propagation may be effected either 
from seeds or by the division of the roots; but, 
when conducted in the latter method, it rapidly 
induces degeneracy.— Upwards of a dozen species 
of columbine, ail ornamental, most about 15 or 
20 inches high, and the majority with purple or 
blue flowers, have been introduced from Siberia, 
Switzerland, and similar countries; and six of 
these are enumerated in Mawe’s systematic cata- 
| logue of choice plants,—A. viscosa, bicolor, alpina, 
canadensis, atropurpurea, and viridiflora. 
COLUMBIUM. An elementary metallic sub- 
stance. It was discovered in 1801; it exists, in 
most of its ores, as an acid in union with the 
oxides of iron and manganese; and it combines 
| with other elements, particularly oxygen, chlo- 
rine, and sulphur; but it is neither plentiful nor 
| peculiar enough to be of much consequence to 
. | white, and crimson flowers. Some species of the 
the arts. It is obtained in the form of a black 
powder, and acquires the metallic lustre from 
compression. 
COLUMBO. See Catumpa. 
COLURNA. See Hazen. 
COLUTEA. See Buapprr-Senwa. 
~COLZA. See Cozz. 
COMARUM. See Crnqueroin (Mans). 
COMBRETUM. A genus of ornamental tropi- 
cal plants, forming the type of the natural order 
Combretaceze. This order comprises the genera 
combretum, quisqualis, terminalia, bucida, cono- 
carpus, getonia, and poivrea; and it has, within 
the gardens of Great Britain, about 40 species,— 
nearly all tropical. Some of the species of com- 
bretum and quisqualis are most magnificent 
climbing plants, and, in their native country, 
adorn the trees of the forest with festoons of 
noble foliage, and garlands of brilliantly yellow, 
COMBUSTION. 
847 
order are officinal; and the nutty fruits of sev- 
eral are esculent.—Seven or eight species of the 
genus combretum were introduced to our hot- 
houses between 1818 and 1826; and about 40 
other species have been scientifically described. 
The dwarf and the large-flowered, C. nanum and 
C. grandiflorum, are evergreen shrubs,—the for- 
mer two feet high, with white flowers, and the 
latter from 5 to 10 feet high, with scarlet flow- 
ers; and all the other introduced species—as 
well as about half a dozen which have been 
transferred to other genera—are climbers of 
great height and surprising beauty. 
COMBUSTION. It is not easy to give a cor- 
rect definition, or to assign a general cause, of 
this familiar phenomenon. It may, however, be 
described as the result of the combination of two 
or more bodies, attended with a disengagement 
of heat and light. This description distinguishes 
combustion from zgnztzon, which is merely the 
result of an elevation of the temperature, with- | 
out any chemical combination. Fire was for- 
merly considered as an element, which had the 
power of converting certain bodies into its own | 
nature ; but the progress of chemical science soon 
showed the error of this notion. Stahl’s cele- 
brated theory was founded on the hypothesis of 
the existence of a substance which he called 
phlogiston. Every combustible body was sup- 
posed to contain this substance, which was dis- 
engaged by combustion: the loss of the phlogis- 
ton was the cause of the residuum being incom- 
bustible. 
moment of its disengagement. The discoveries 
of Black and Priestley opened the way to the 
system of Lavoisier, which, in 1785, entirely sup- 
planted the theory of Stahl. During the conver- 
sion of solids into fluids, and of fluids into vapours, 
there is a considerable absorption of heat : when, 
on the contrary, vapours and liquids are restored | 
to the fluid and solid form, the heat which they 
contain is evolved, and passes from the latent to 
the sensible state. See Conortc. These views 
were assumed by Lavoisier as the basis of his the- 
ory. Oxygen gas was considered as a compound 
of a peculiar basis, united to the matter of light 
and heat, and combustion as the combination of 
oxygen with the burning body. During the com- 
bustion, the basis, combining with the combusti- 
ble, augmented its weight and changed its pro- 
perties; while the imponderable elements of the 
gas—light and heat—were developed in the form 
of flame. But facts prove this theory incorrect 
In the first place, all the phenomena of combus- 
tion take place, in many cases, without the pre- 
sence of oxygen. In the second place, there are 
many cases in which oxygen unites with bodies, 
without the evolution of light and heat, as dur- 
ing the change of some metals on exposure to the 
air. And, further, there are many instances in 
which combustion takes place not only without 
condensation, but where gaseous matter is actu- 
The heat and light were attributed to | 
the violent agitation of the phlogiston at the | 
