The lungs of birds have several openings, communicating with
corresponding air-bags or cells, which fill the whole cavity of the body
from the neck downwards, and into which the air passes and re-passes in
the process of breathing. This is not all: the very bones of birds are
hollowed out with the design of receiving air from the lungs, from which
air-pipes are conveyed to the most solid parts of the body, and even
into the quills and plumelets of the feathers, which are hollow or
spongy for its reception. As all these hollow parts, as well as the
cells, are only open on the side communicating with the lungs, the bird
requires only to take in a full breath to fill and distend its whole
body with air, which, in consequence of the considerable heat of its
body, is rendered much lighter than the air of the atmosphere. By
forcing this air out of the body again, the weight becomes so much
increased, that birds of large size can dart down from great heights in
the air with astonishing velocity. The structure of insects is not a
little analogous.—_Ins. Trans._
AIR-GUN, _s._ A species of gun charged with air instead of powder.
[Illustration]
The _air-gun_, although long known, has never been much used, as its
slight report is the only advantage it can possess over fire-arms, while
its danger and inefficiency are admitted. Fatal accidents have occurred
in charging it, and every attempt to remedy the danger has been
unsuccessful. In the old principle, the globe or ball which forms the
receiver has frequently blown up while the air was being pumped in, and
loss of life or severe injury resulted. Latterly, the attention of
several experimentalists has been directed to its improvement. One of
them, Mr. Laing, of the Haymarket, imagined he had overcome the great
objection; and by a very ingenious alteration, in which the globe was
done away with, and the air-receiver transferred to the stock of the
gun, he hoped thus to have removed the danger. But in this he was sadly
disappointed. While trying the improved air-gun, the receiver burst,
injured him severely, and induced him to abandon any farther experiments
with this dangerous instrument.
Indeed, the manifest inferiority of the air-gun to the rifle, would,
independently of its danger, prevent it from coming into general use. As
an instrument, it is extremely troublesome to shoot with, and liable to
constant derangement. Its power is very weak, and in accuracy of aim the
rifle is far superior. Even the advantage of slight report in the
discharge is now comparatively done away with, in consequence of the
recent introduction of the small-bore rifles for rook and rabbit
shooting; which, from the trifling quantity of powder used in charging,
are scarcely louder than the air-gun.
Purday, whose reputation as a rifle maker is deservedly high, has
brought them to great perfection; and some beautiful guns of this
description may be seen at his manufactory, which, though so small in
the gage as to require bullets eighty to the pound, are perfect alike in
execution and workmanship.
With respect to the _Air-cane_, though a more recent invention, it is
only necessary to say, that it has all the disadvantages of the air-gun,
with much weaker power, and a greater liability to get out of order. It
is a mere toy, and, certainly, a very dangerous one.
* * * * *
Formerly, poachers were in the habit of using air-guns to destroy
pheasants in the preserves. The instrument made no noise, and the
operator preferred the boisterous, rainy night, when the moon was nearly
at the full; the wet did not in the least affect the discharge of this
implement, and the keepers knew a common gun could not be effectually
employed in such tempestuous weather; besides, the report caused
immediate alarm, and frequent detection. Vast numbers of pheasants were
carried off, before this practice was discovered.
The late Mr. Tyssen was partial to an air-gun for shooting rooks,
rabbits, &c., and was using one at Donyland Park, in Essex, when the
screw of the valve gave way, as the servant was pumping the air into it;
the copper ball fortunately took such a direction, that no one was hurt;
but, in passing through the trees, it cut off some considerable
branches. This accident staggered his confidence in the security of
their principle, and from the best informed persons he consulted upon
the subject, he was convinced there was no certainty of their being
safe, and he wisely relinquished the air-gun, with all its asserted
superlative properties.—_Daniel._
AIRY, _a._ Composed of air; relating to the air; high in air; light
as air; gay, sprightly, full of mirth, lively.
ALCOHOL, _s._ A highly rectified spirit of wine.
ALKALI, _s._ Any substance which combines with an acid, and produces
a salt.
_Alkalies_ form one of the classes of saline bodies, and are of three
kinds: the _vegetable alkali_—kali, or potash,—the _mineral
alkali_—soda, or natron,—and the _volatile alkali_, or ammonia.
_Alkalies_ are distinguished by their changing blue vegetable colours to
a green, and yellow to orange; by combining rapidly with acids, and
forming with them neutral salts—and by rendering oils miscible with
water. _Vegetable_ and _mineral alkalies_, not being evaporable, except
in a high degree of heat, are termed _fixed_: and _ammonia_, being
evaporable in a low temperature, obtains the name of _volatile
alkali_.—_White._
ALKALINE, _a._ That which has the qualities of alkali.
ALLSPICE, _s._ Jamaica pepper, a powerful cordial and carminative;
the dose from two to three or four drachms. Mr. Bracey Clarke,
in a book he has published on flatulent or spasmodic colic, or
gripes, strongly recommends a tincture of allspice in proof
spirit, as an effectual remedy for that disorder. The dose about
4 to 6 oz. in water.
ALLURE, _v._ To entice to any thing.
ALOES, _s._ A precious wood used in the east for perfumes, of which
the best sort is of higher price than gold; a tree which grows
in hot countries; a medicinal juice extracted from the common
aloes tree.
Aloes is the inspissated juice of a plant of the same name, and is an
effectual purgative for horses. It is intensely bitter, and strong and
unpleasant to the smell.
Socotrine aloes is grown in the island Socotra, and is safer in its
operation than the other kinds. It is of a dark reddish or brown colour,
opaque, and less disagreeable to smell than the others. It formerly sold
at a high price, and was therefore liable to adulteration. Barbadoes
aloes is a coarser medicine, liable to produce griping, and other
unpleasant effects; but it is a safe and efficacious purgative. It is
darker coloured, less brittle, and of a stronger and more disagreeable
smell—more active than the Socotrine; and considered more certain in its
operation. Every kind of aloes is liable to produce bad consequences if
given too largely, or if the horse be treated improperly while under its
effect. There is a peculiarity in the horse’s intestines which renders
them more liable to be injured by purgatives than those of other
domestic animals, and therefore cathartic medicines should be prepared
by persons of judgment and experience.
Cape aloes is rather transparent, very brittle, easily powdered, in this
state of a bright yellow colour; the odour arising from it is not so
strong as the Barbadoes, but stronger and less agreeable than the
Socotrine. This kind is sold at a much lower price than the others, but
is so weak and uncertain in its effect, that it is seldom employed in
veterinary medicine. The dose of Socotrine aloes is from five to nine,
Barbadoes from four to six, and Cape from six to ten drachms.
Aloes operates more speedily when united with soap, or any of the fixed
alkalies. In old books cream of tartar is prescribed with aloes, under
the supposition that it prevented griping, but soap is preferable.
Aloes is sometimes given as an alterative in doses of one or two
drachms. It is also an ingredient in Friar’s balsam, and compound
tincture of myrrh; preparations much used by farriers.—_White._