His Commentary on the Epistle to the Philippians (1618,
reprinted 1864) is a specimen of his preaching before his
college, and of his fiery denunciation of popery and his
fearless enunciation of that Calvinism which Oxford in common
with all England then prized. In 1598 he was chosen provost
of his college, and in 1606 was vice-chancellor of the
university. In the discharge of his vice-chancellor's duties
he came into conflict with Laud, who even thus early was
manifesting his antagonism to the prevailing Puritanism.
He was also rector of Otmore (or Otmoor), near Oxford, a living
which involved him in a trying but successful litigation,
whereof later incumbents reaped the benefit. He died on
the 6th of October 1610. His character as a man, preacher,
divine, and as an important ruler in the university, will be
found portrayed in the Epistle by John Potter, prefixed to
the Commentary. He must have been a fine specimen of the
more cultured Puritans --possessed of a robust common-sense
in admirable contrast with some of his contemporaries.
AIRD, THOMAS (1802-1876), Scottish poet, was born at Bowden,
Roxburghshire, on the 28th of August 1802. He was educated at
Edinburgh University, where he made the acquaintance of Carlyle
and James Hogg, and he decided to devote himself to literary
work. He published Martzoufie, a Tragedy, with other Poems
(1826), a volume of essays, and a long narrative poem in
several cantos, The Captive of Fez (1830). For a year he
edited the Edinburgh Weekly Journal, and for twenty-eight
years the Dumfriesshire and Galloway Herald. In 1848 he
published a collected edition of his poems, which met with much
favour. Carlyle said that he found in them ``a healthy breath
as of mountain breezes.'' Among Aird's other friends were De
Quincey, Lockhart, Stanley (afterwards dean of Westminster) and
Motherwell. He died at Dumfries on the 25th of April 1876.
AIRDRIE, a municipal and police burgh of Lanarkshire,
Scotland. Pop. (1901) 22,228. It is situated 11 m. E. of
Glasgow by the North British railway, and also communicates with
Glasgow by the Monkland Canal (which passes within 1 m. of the
town), as well as by the Caledonian railway via Coatbridge and
Whiffiet. The canal was constructed between 1761 and 1790,
and connects with the Forth and Clyde Canal near Maryhill.
Airdrie was a market town in 1695, but owes its prosperity to
the great coal and iron beds in its vicinity. Other industries
include iron and brass foundries, engineering, manufactures
of woollens and calicoes, silk-weaving, paper-making, oil and
fireclay. The public buildings comprise the town hall, county
buildings, mechanics' institute, academy, two fever hospitals
and free library, the burgh having been the first town in
Scotland to adopt the Free Library Act. Airdrie unites with
Falkirk. Hamilton, Lanark and Linlithgow in sending one member to
parliament. The parish of New Monkland, in which Airdrie
lies, was formed (with Old Monkland)in 1640 out of the ancient
barony of Monkland, so named from the fact that it was part
of the lands granted by Malcolm IV. to the monks of Newbattle.
AIRE, a town of south-western France, in the department
of Landes, on the left bank of the Adour, 22 m. S.E. of
Mont-de-Marsan on the Southern railway between Morcenx and
Tarbes. Pop. (1906) 2283. It is the seat of a bishopric, and
has a cathedral of the 12th century and an episcopal palace of
the 11th, 17th and 18th centuries. Both have undergone frequent
restoration. They are surpassed in interest by the church
of St Quitterie in Mas d'Aire, the suburb south-west of the
town. The latter is a brick building of the 13th and 14th
centuries, with a choir in the Romanesque style, and a fine
western portal which has been much disfigured. The crypt
contains several Gallo-Roman tombs and the sarcophagus (5th
century) of St Quitterie. Aire has two ecclesiastical seminaries.
Aire (Atura, Vicus Julii) was the residence of the kings of
the Visigoths, One of whom, Alaric II. (q.v.), there drew
up his famous code. The bishopric dates from the 5th century.
AIRE, a town of northern France, on the river Lys, in the
department of Pas-de-Calais, 12 m. S.S.E. of St Omer by
rail. Pop. (1906) 4258. The town lies in a low and
marshy situation at the junction of three canals. The
chief buildings are the church of St Pierre (15th and 16th
centuries), which has an imposing tower and rich interior
decoration; a hotel de ville of the 18th century; and the
Bailliage (16th century), a small building in the Renaissance
style. Aire has flour-mills, leather and oil works, and
nail manufactories, and trade in agricultural produce.
In the middle ages Aire belonged to the counts of Flanders,
from whom in 1188 it received a charter, which is still
extant. It was given to France by the peace of Utrecht 1713.
AIR-ENGINE, the name given to heat-engines which use air for
their working substance, that is to say for the substance which
is caused alternately to expand and contract by application
and removal of heat, this process enabling a portion of the
applied heat to be transformed into mechanical work. Just
as the working substance which alternately takes in and gives
out heat in the steam-engine is water (converted during a
part of the action into steam), so in the air-engine it is
air. The practical drawbacks to employing air as the working
substance of a heat-engine are so great that its use has been very
limited. Such attempts as have been made to design air-engines
on a large scale have been practical failures, and are now
interesting only as.steps in the historical development of
applied thermodynamics. In the form of motors for producing
very small amounts of power air-engines have been found
convenient, and within a restricted field they are still met
with. But even in this field the competition of the
oil-engine and the gas-engine is too formidable to leave to
the air-engine more than a very narrow chance of employment.
One of the chief practical objections to air-engines is the
great bulk of the working substance in relation to the amount
of heat that is utilized in the working of the engine. To
some extent this objection may be reduced by using the air
in a state of compression, and therefore of greater density,
throughout its operation. Even then, however, the amount of
operative heat is very small in comparison with that which
passes through the steam-engine, per cubic foot swept through
by the piston, for the change of state which water undergoes
in its transformation into steam involves the taking in of
much more heat than can be communicated to air in changing its
temperature within such a range as is practicable. Another
and not less serious objection is the practical difficulty
of getting heat into the working air through the walls of the
containing vessel. The air receives heat from an external
furnace just as water does in the boiler of a steam-engine,
by contact with a heated metallic surface, but it takes up
heat from such a surface with much less readiness than does
water. The waste of heat in the chimney gases is accordingly
greater; and further, the metallic shell is liable to be
quickly burned away as a result of its contact at a high
temperature with free oxygen. The temperature of the shell
is much higher than that of a steam boiler, for in order to
secure that the working air will take up a fair amount of
heat, the upper limit to which its temperature is raised
greatly exceeds that of even high-pressure steam. This
objection to the air-engine arises from the fact that the
heat comes to it from external combustion; it disappears
when internal combustion is resorted to; that is to say,
when the heat is generated within the envelope containing
the working air, by the combustion there of gaseous or other
fuel. Gas-engines and oil-engines and other types of engine
employing internal combustion may be regarded as closely
related to the air-engine. They differ from it, however, in
the fact that their working substance is not air, but a mixture
of gases--a necessary consequence of internal combustion. It
is to internal combustion that they owe their success, for it
enables them to get all the heat of combustion into the working
substance, to use a relatively very high temperature at the
top of the range, and at the same time to escape entirely
the drawbacks that arise in the air-engine proper through the
need of conveying heat to the air through a metallic shell.
A form of air-engine which was invented in 1816 by the
Rev. R. Stirling is of special interest as embodying the
earliest application of what is known as the ``regenerative''
principle, the principle namely that heat may be deposited
by a substance at one stage of its action and taken up again
at another stage with but little loss, and with a great
resulting change in the substance's temperature at each of the
two stages in the operation. The principle has since found
wide application in metallurgical and other operations. In
any heat-engine it is essential that the working substance
should be at a high temperature while it is taking in heat,
and at a relatively low temperature when it is rejecting
heat. The highest thermodynamic efficiency will be reached
when the working substance is at the top of its temperature
range while any heat is being received and at the bottom while
any heat is being rejected--as is the case in the cycle of
operations of the theoretically imagined engine of Carnot.
(See THERMODYNAMICS and STEAM-ENGINE.) In Carnot's cycle
the substance takes in heat at its highest temperature, then
passes by adiabatic expansion from the top to the bottom of
its temperature range, then rejects heat at the bottom of the
range, and is finally brought back by adiabatic compression
to the highest temperature at which it again takes in heat,
and so on. An air-engine working on this cycle would be
intolerably bulky and mechanically inefficient. Stirling
substituted for the two stages of adiabatic expansion and
compression the passage of the air to and fro through a
``regenerator,'' in which the air was alternately cooled
by storing its heat in the material of the regenerator and
reheated by picking the stored heat up again on the return
journey. The essential parts of one form of Stirling's engine
are shown in fig. 1. There A is the externally fired heating
vessel, the lower part of which contains hot air which is
taking in heat from the furnace beneath. A pipe from the
top of A leads to the working cylinder (B). At the top of
A is a cooler (C) consisting of pipes through which cold
water is made to circulate. In A there is a displacer (D)
which is connected (by parts not shown) with the piston in
such a manner that it moves down when the piston has moved
up. The air-pressure is practically the same above and
below D, for these spaces are in free communication with
one another through the regenerator (E), which is an annular
space stacked loosely with wire-gauze. When D moves down,
the hot air is driven up through the regenerator to the upper
part of the containing vessel. It deposits its heat in the
wire-gauze, becoming lowered in temperature and consequently
reduced in pressure. The piston (B) descends, and the air,
now in contact with the cooling pipes (C), gives up heat to
them. Then the displacer (D) is raised. The air passes down
through its regenerator, picking up the heat deposited there,
and thereby having its temperature restored and its pressure
raised. It then takes in heat from the furnace, expanding in
