A 
| gaseous state. 
| state of our knowledge, that they may be attri- 
_ buted to the disengagement of the electric fluid. 
| borage tribe. 
een eve vont nar ee ere 
ally produced from solid matter, as in the inflam- 
mation of gunpowder. Besides, the evolution of 
light, if it were derived from the gas, should be 
proportional to the quantity solidified, whereas 
it depends chiefly on the combustible. The first 
of these objections to Lavoisier’s theory, which is 
yet generally received, has been partly removed 
by modifying the definition so as to extend it to 
several other bodies, hence called supporters of 
combustion. The definition which we have given 
of this phenomenon at the beginning of this ar- 
ticle is merely. a description. The question 
arises, Whence come the light and heat? They 
are generally referred to the condensation which 
is almost always a necessary consequence of a 
chemical combination ; but we have already seen 
that, in some cases, they are produced where the 
component parts actually pass from a solid to a 
It seems probable, in the present 
“In every chemical combination,” says Berzelius, 
“ there is a neutralization of opposite electricities, 
and this neutralization produces the heat and 
light in the same manner as it does in the Ley- 
den jar or the galvanic battery.” But to this it 
may be objected, that, if electricity were the 
cause of the disengagement of the heat and light, 
they would always bear a fixed proportion to 
each other. This isnot the case: the combustion 
of oxygen and hydrogen disengages a very great 
quantity of caloric, but very little light; that of 
phosphorus and oxygen produces opposite results. 
There is, then, no theory of combustion, at pre- 
sent ae en will explain all the circum- 
stances of this phenomenon. If there be any one 
general cause, it must be one which, like affinity, 
is modified by the nature of the agents and the 
peculiar circumstances of their mutual action. 
COMEFREY,—botanically Symphytum. A ge- 
nus of hardy, perennial, herbaceous plants, of the 
The very rough species, Symphy- 
tum asperrumum, was introduced to Britain from 
the Caucasian mountains in 1799, and has, for a: 
~ number of years past, drawn the attention of ag- 
riculturists as probably a valuable forage plant. 
Its root is tuberculated, branching, thick, and 
fleshy ; its stem is very prickly and from 6 to 10. 
feet high; its leaves are rough-stalked, heart- 
shaped, broad, tapering to a point, and of a blu- 
ish-green colour; its flowers are cylindrical with 
a campanulate inflated limb, and have a change- 
ably blue and red colour, and appear from May 
till September ; and its seeds are naked, gibbous, 
and not pierced at the base. Both its root and 
its stem are very farinaceous; its root is probably 
as esculent as that of Stachys palustris; its stem 
has sometimes been blanched and eaten like that 
of angelica; and its shoots and leaves, during all 
the period intermediate between the seedling and 
the hardened conditions of the plant, are greedily 
eaten by cows. It was brought into notice as an 
agricultural plant, by Mr. D. Grant, a nursery- 
COMFREY. 
man of Lewisham, and was introduced to Ireland, 
and recommended to the cottier-farmers of that 
country, about eight years ago, by Dr. Derenzy. 
Young mentions it in his Farmer’s Calendar, 
under the name of trottles, and appears to think 
that the whole plant is valuable; but Dr. Derenzy 
supposes the roots to be useless for either man or 
beast, and recommends the plant solely for shoots 
and foliage. It is easily propagated; and, when 
once established, it will, without any renewal, 
produce enormous crops for many years. 
slowly to maturity; but its roots possess the 
power of facile and rapid reproduction, and may, 
at any time from October to April, but especially 
in February or March, be taken up, cut into 
small pieces, and set in drills at distances of two 
feet from drill to drill and 15 inches from plant 
to plant. The plant will thrive in poor, dry, ex- 
posed soil; yet it ought, if possible, to have good 
deep soil, se will well repay an abundant dose 
of manure; and as it yields large and constant 
produce for a long series of years, it requires, of 
course, to be grown apart from any course of 
rotation. It should be cut about the time of 
flowering, and never allowed to go to seed. Its 
ordinary annual produce, in green fodder, was 
estimated by Mr. Grant, and has since been esti- 
mated by practical agriculturists, at about 30 
tons per acre; and, in an experiment on the farm 
of. Carnew Castle in Ireland, it amounted to the 
enormous quantity of 82 tons per Irish acre, in: | 
three cuttings of 284 tons in the middle of April, 
31 in the middle of July, and 225 in the middle 
of September. It is preferred to vetches by pigs ; 
it is not, like clover, dangerous to cows or sheep; 
and it does not communicate any bad flavour to 
cows’ milk. 
originated in 1825. 
sented in Plate X XJ. 
The officinal comfrey, Symphytum officinale, is 
indigenous in Britain, and may be found by the 
sides of ditches and ‘in other moist situations. 
Its root is tuberous, thick, full of a slimy juice, 
externally black, and internally white; its stem 
The normal plant is repre- 
is erect, thick, and usually about 4 feet high ; its” 
leaves are long, pointed, rough, and deep green; - 
and its flowers are generally white, yet often red- | 
dish, and appear from May till July. The slimy 
mucilaginous matter of the root has sometimes 
been used in medicine as a demulcent, and has 
acquired for the plant its specific botanic desig- 
nation; but it is of very little value. A variety 
of this species, known as S, 0. patens, attains the 
same height as the normal plant, and carries 
blue-coloured flowers.—The tuberous species, 
Si ymphytum tuberosum, grows wild in moist shady 
places in Scotland. Its root is tuberous; its 
stem is knobbed, branched, and 3 or 4 feet high ; 
and its flowers are drooping, have a yellowish 
white colour tinged with green, and appear from 
May till October.—Seven species, besides the very 
rough, have been introduced from foreign coun- 
Its , 
seeds seldom ripen, and its seedling plants grow |. 
A small hybrid variety of it was: 
