468 BOG-ORCHIS. 
clays or other impervious substrata, by the silty 
sediments of streams flowing remotely from bogs. 
Artificial imitations of it—-in many instances 
very similar to itself in ultimate composition, 
and little if at all inferior in manurial action— 
are often made by mixing the light mud of ponds 
and ditches with leaves, weeds, and grasses, in 
pits or little reservoirs, frequently turning and 
watering the mixture, and finally exposing it in 
heaps to the air till it acquires the requisite 
consolidation and pulverulence. The kind of 
bog earth, which forms a suitable ingredient of 
coarse composts for field farming, is more fre- 
quently designated peat earth or simply peat, 
and consists simply of the more compact or peaty 
portions of bogs, laid open to the weather till 
they become dry and powdery. 
BOG-ORCHIS,—botanically d/alavis. A genus 
of herbaceous plants, of the orchis tribe. The 
marsh species, Malaxis paludosa, is a perennial, 
of delicate appearance, and grows wild in the 
wet spongy bogs of England. Its root is bulbous, 
| and increases by offsets ; its stem is angular, 
| smooth, and about 3 inches high, and is one of 
the smallest belonging to our native orchidez ; 
its leaves are ovate, various in length, and three 
or four in number; and its flowers are produced 
at the top of the stem in a dense cluster, have 
a yellowish-green colour, and appear in July. 
About a dozen other species are known to bo- 
tanists ; but none of them grow or are cultivated 
in Great Britain. 
BOG-RUSH,—hbotanically Schenus. 
of grassy-looking plants, of the rush tribe. 
A genus 
The 
blackish species, Schenus mgricum, grows wild 
on the spongy bogs of Britain. Its root has a 
comparatively great length, and consists of 
strong fibres, crowned with erect, folded, glossy- 
black sheaths; its leaves are upright, acute, 
and very narrow, and arise from some of the 
sheaths at the crown of the root; the stem is 
chiefly naked, but partly embraced by the 
sheaths, and shaded by the leaves, and attains a 
height of about a foot; and the flowers have 
long yellow anthers and dark purple stigmas, 
and appear in July. Three halftender species 
were introduced a few years ago from New Hol- 
land and the West Indies; and a hardy species, 
Schenus mucranatus, was introduced about sixty 
years ago from the south of Europe. Upwards 
of sixty other species are known to botanists. 
BOG-SPAVIN. A soft tumour, ofthe nature 
of a windgall, on the hock of the horse. Dr. 
Bracken regarded it as a collection within a bag 
or cyst of the brownish, gelatinous, or mucous 
matter which naturally serves for lubricating 
the joint,—the common membrane which en- 
closes the joint forming the cyst; and he illus- 
trates both the disease itself and the mode of 
treating it by an instance which occurred in a 
young colt of his own. He found that, by press- 
ing the spavin hard on the inside of the hock, a 
small tumour appeared on the outside, and he 
BOILING. 
therefore concluded that the disease had its seat 
in the inside; and he cut into it, discharged 
a large quantity of the glutinous or mucous 
matter, dressed the sore with dossils.dipped in 
oil of turpentine, and put into it, on every third 
or fourth day, a powder composed of calcined 
vitriol, alum, and bole. By this treatment, the 
tumour sloughed off, and came away; and a com- 
plete cure was effected without leaving any scar. 
But a less critical method, and indeed the only 
one with which any ordinarily bad case of bog- 
spavin can be prudently attacked, is, by means 
of blistering or of firing, to excite the absorbent 
vessels in the interior of the limb, and imme- 
diately around the seat of the disease, to carry 
away the encysted fluid which constitutes the 
tumour. The majority of cases, however, will 
resist even this method; and all cases occurring 
in the draught-horses of a farm, or in any other 
horses not required for rapid action, ought to be 
entirely let alone. Bog-spavin often induces 
permanent though not very great lameness; it 
is, in every instance, a decided unsoundness in a 
horse ; and when removed by skilful medical 
treatment, it is very liable to be reinduced. 
BOIL. An inflamed and suppurating tumour 
in any of the fleshy parts of cattle or sheep. A 
boil ought:to be brought to a head by the appli- 
cation to it of a plaster composed of wheat flour, 
yolks of eggs, and tar; and when it feels soft to 
the touch, it ought to be opened with a lancet, 
in order that the purulent matter may escape. 
Hllis recommends that, after it has been opened 
and freed from pus, it first be anointed .with 
ointment of tobacco, and next covered with a 
plaster made of equal parts of turpentine, burnt 
salt, honey, and galbanum, and about a quarter 
more than.an equal part of resin. 
BOILING, or Esunurrion. The rapid expan- 
sion of a liquid by heat, and violent escape of 
successive portions of it in the form of vapour. 
In ordinary evaporation, a liquid passes off slowly, 
quietly, and insensibly ; but in boiling or ebulli- 
tion, it escapes rapidly, tumultuously, and very 
visibly—halls of vapour rising from the bottom or 
sides of the body of the liquid, of so great size and 
in such swift succession, as to cause a tumbling 
commotion through all the interior, and a cloud- 
ing aloft of steam from the top. The heat re- 
quisite to produce ebullition, or what is techni- 
cally called the boing point of liquids, widely 
varies in different kinds of liquids, and is con- 
siderably affected in any one liquid by some 
modifying conditions. The boiling point of sul- 
phuric ether, in ordinary circumstances, in the 
open air is 96° of Fahrenheit; of alcohol, 176° ; 
of water, 212°; of oil of turpentine, 316°; and of 
mercury, 662°; and, in the case of any one li- 
quid, it is uniform in the same circumstances, or 
under the same conditions, but suffers variation 
when some of the circumstances or conditions 
are altered. For example, when the barometer 
stands at 30 inches, water boils at 212° in a me- 
