whitish underneath ; on foot-stalks an inch 
in length ; at these joints, which are far 
asunder, come out also small side branches, 
growing erect ; they, as well as the stem, 
are terminated by loose panacles of flesh- 
coloured flowers, succeeded by oblong glu- 
tinous seeds. This plant is found at La 
Vera Cruz, also in the Society Isles. 
BOILING. When all other circum- 
stances are the same, the evaporation of 
liquids increases with their temperature; 
and after they are heated to a certain tem- 
perature, they assume the form of elastic 
fluids with great rapidity. If the heat be 
applied to the bottom of the vessel contain- 
ing the liquids, as is usually the case, after 
the whole liquid has acquired this tempera- 
ture, those particles of it which are next 
the bottom become an elastic fluid first : 
they rise up, as they are formed, through 
the liquid, like air bubbles, and throw the 
whole into violent agitation. The liquid is 
then said to ' boil. Every particular liquid 
has a fixed point at which this boiling com- 
mences (other things being the same) ; and 
this is called the boiling point of the liquid. 
Thus, water begins to boil when heated to 
212°. It is remarkable, that after a liquid 
has begun to boil, it never becomes any 
hotter, however strong the fire be to which 
it is exposed. A strong heat indeed makes 
it boil more rapidly, but does not increase 
its temperature. This was first observed 
by Dr. Hooke. The following table con- 
tains the boiling point of a number of li- 
quids. 
Bodies. Boiling point. 
Ether 98° 
Ammonia , 140 
Alcohol 176 
Water 212 
Muriate of lime 230 
Nitric acid 248 
Sulphuric acid 590 
Phosphorus 554 
Oil of turpentine 560 
Sulphur 570 
Linseed oil 600 
Mercury 660 
It will be seen when we come to treat of 
the melting point of solids, that it is capa- 
ble of being varied considerably by altering 
the situation of the body. Thus, water 
may be cooled down considerably lower 
than 32° without freezing. The boiling 
point is still less fixed, depending entirely 
on the degree of pressure to which the liquid 
to be boiled is exposed. If we diminish the 
pressure, the liquid boils at a lower tempera- 
ture ; if we increase it, a higher tempera- 
ture is necessary to produce ebullition. From 
the experiments of Professor Robinson, it 
appears that, in a vacuum, all liquids boil 
about 145° lower than in the open air, under 
a pressure of 30 inches of mercury ; there- 
fore water would boil in vacuo at 67°, and 
alcohol at 34°. In a Papin’s digester, the 
temperature of water may be raised to 
300°, or even 400°, without ebullition ; but 
the instant that this grqat pressure is re- 
moved, the boiling commences with pro- 
digious violence. 
BOLETUS, in botany, so called from 
its globular form, characterized by Linnmus 
as a horizontal fungus ; porous, or punched, 
with lobes underneath. In the fourteenth 
edition of the “ Systema Naturae,” only 
twenty-one species are recited, eleven of 
which are parasitical and stemless, the rest 
are stipitated. From B. igniarius is pre- 
pared the amadou, commonly used on the 
continent for tinder, to receive the spark 
struck from the steel by the flint, and the 
agaric for stopping haemorrhages in ampu- 
tations, &c. 
BOLT, among builders, an iron fastening 
fixed to doors and windows. They are ge- 
nerally distinguished into three kinds, viz. 
plate, round, and spring bolts. 
Bolts, in gunnery, are of several sorts, 
as, 1. Transom bolts, that go between the 
cheeks of a gun-carriage to strengthen the 
transums. 2. Prise bolts, the large knobs of 
iron on the cheeks of a carriage which 
keep tlie hand-spike from sliding when it is 
poized up the breech of a piece. 3. Tra- 
verse bolts, the two short bolts that being 
put one in each end of a mortar carriage, 
serve to traverse her. 4. Bracket bolts, 
the bolts that go through the cheeks of a 
mortar, and by the help of quoins keep her 
fixed at the given elevation. And, 5. Bed 
bolts, the four bolts that fasten the brackets 
of a mortar to the bed. 
Bolts, in a ship, are iron pins, of which 
there are several sorts according to their 
different make and uses. Such are : drive 
bolts, used to drive out others ; ray bolts, 
with jags or barbs on each side to keep 
them from flying out of their holes ; clench 
bolts, which are clenched with rivetting 
hammers ; forelock bolts, which have at the 
end of a forelock of iron driven in to keep 
them from starting back; set bolts, used 
for forcing the planks and bringing them 
close together ; fend or fender bolts, made 
