henceforth he calls himself ``rex totius Britanniae.'' About
this time (the exact chronology is uncertain) AEthelstan expelled
Sihtric's brother Guthfrith, destroyed the Danish fortress at
York, received the submission of the Welsh at Hereford, fixing
their boundary along the line of the Wye, and drove the Cornishmen
west of the Tamar, fortifying Exeter as an English city.
In 934 he invaded Scotland by land and sea, perhaps owing to
an alliance between Constantine and Anlaf Sihtricsson. The
army advanced as far north as Dunottar, in Kincardineshire,
while the navy sailed to Caithness. Simeon of Durham
speaks of a submission of Scotland as a result; if it
ever took place it was a mere form, for three years later
we find a great confederacy formed in Scotland against
AEthelstan. This confederacy of 937 was joined by Constantine,
king of Scotland, the Welsh of Strathclyde, and the
Norwegian chieftains Anlaf Sihtricsson and Anlaf Godfredsson,
who, though they came from Ireland, had powerful English
connexions. A great battle was fought at Brunanburh (perhaps
Brunswark or Birrenswark hill in S.E. Dumfriesshire), in
which AEthelstan and his brother Edmund were completely
victorious. England had been freed from its greatest danger
since the days of the struggle of Alfred against Cuthrum.
AEthelstan was the first Saxon king who could claim in any
real sense to be lord paramount of Britain. In his charters
he is continually called ``rex totius Britanniae,'' and he
adopts for the first time the Greek title basileus. This
was not merely an idle flourish, for some of his charters
are signed by Welsh and Scottish kings as subreguli.
Further, AEthelstan was the first king to bring England into
close touch with continental Europe. By the marriage of his
half-sisters he was brought into connexion with the chief
royal and princely houses of France and Germany. His sister
Eadgifu married Charles the Simple, Eadhild became the wife
of Hugh the Great, duke of France, Eadgyth was married to
the emperor Otto the Great, and her sister AElfgifu to a
petty German prince. Embassies passed between AEthelstan and
Harold Fairhair, first king of Norway, with the result
that Harold's son Haakon was brought up in England and is
known in Scandinavian history as Haakon Adalsteinsfostri.
AEthelstan died at Gloucester in 940, and was buried at Malmesbury,
an abbey which he had munificently endowed during his lifetime.
Apparently he was never married, and he certainly had no issue.
A considerable body of law has come down to us in
AEthelstan's name. The chief collections are those issued
at Grately in Hampshire, at Exeter, at Thunresfeld, and the
Judicia civitatis Lundonie. In the last-named one personal
touch is found when the king tells the archbishop how grievous
it is to put to death persons of twelve winters for stealing.
The king secured the raising of the age limit to fifteen.
AUTHORITIES.---Primary: The Saxon Chronicle, sub ann.;
William of Malmesbury, Gestal Regum, i. 141-157, Rolls
Series, containing valuable original information (v. Stubbs'
Introduction, II. lxvii.); Birch, Cartul. Saxon. vol.
ii. Nos. 641-747; A.S. Laws. (ed. Liebermann), i. 146-183;
AEthelweard, Florence of Worcester. Secondary: Saxon
Chronicle (ed. Plummer), vol. ii. pp. 132-142 D.N.B., s.v.
AETHELWEARD (ETHELWARD.) Anglo-Saxon historian, was
the great-grandson of AEthelred, the brother of Alfred and
ealdorman or earl of the western provinces (i.e. probably
of the whole of Wessex). He first signs as dux or ealdorman
in 973, and continues to sign until 998, about which time
his death must have taken place. In the year 991 he was
associated with archbishop Sigeric in the conclusion of a
peace with the victorious Danes from Maldon, and in 994 he
was sent with Bishop AElfheah (Alphege) of Winchester to make
peace with Olaf at Andover. AEthelweard was the author of
a Latin Chronicle extending to the year 975. Up to the year
892 he is largely dependent on the Saxon Chronicle, with
a few details of his own; later he is largely independent of
it. AEthelweard gave himself the bombastic title ``Patricius
Consul Quaestor Ethelwerdus,'' and unfortunately this title
is only too characteristic of the man. His narrative is
highly rhetorical, and as he at the same time attempts more
than Tacitean brevity his narrative is often very obscure.
AEthelweard was the friend and patron of AElfric the grammarian.
AUTHORITIES.---Primary: The Saxon Chronicle, 994 E; Birch,
Cartularium Saxonicum; A.S. Laws (ed. Liebermann), pp. 220-224;
Tabii Ethelwerdi Chron., Mon. Hist. Brit. 449-454. Secondary:
Plummer, Saxon Chronicle, vol. ii. p. ci.; Napier and Stevenson,
Crawford Charters, pp. 118-120; D.N.B., s.v. (A. law.)
AETHELWULF, king of the West Saxons, succeeded his father
Ecgberht in A.D. 839. It is recorded in the Saxon Chronicle
for 825 that he was sent with Eahlstan, bishop of Sherborne,
and the ealdorman Wulfheard to drive out Baldred, king of
Kent, which was successfully accomplished. On the accession of
AEthelwulf, AEthelstan, his son or brother, was made sub-king
of Kent, Surrey, Sussex and Essex. AEthelwulf's reign was
chiefly occupied with struggles against the Danes. After the
king's defeat 843-844, the Somerset and Dorset levies won a
victory at the mouth of the Parret, c. 850. In 851 Ceorl,
with the men of Devon, defeated the Danes at Wigganburg, and
AEthelstan of Kent was victorious at Sandwich, in spite of
which they wintered in England that year for the first time.
In 851 also AEthelwulf and AEthelbald won their great victory at
Aclea, probably the modern Ockley. In 853 AEthelwulf subdued
the North Welsh, in answer to the appeal of Burgred of Mercia,
and gave him his daughter AEthelswith in marriage. 855 is the
year of the Donation of AEthelwulf and of his journey to Rome
with Alfred. On his way home he married Judith, daughter
of Charles the Bald. According to Asser he was compelled
to give up Wessex to his son AEthelbald on his return, and
content himself with the eastern sub-kingdom. He died in 858.
Chronicle, s.a. 823, 836, 840, 851, 853, 855. (F. G. M. B.)
AETHER, or ETHER (Gr. aither, probably from aitho,
burn, though Plato in his Cratylus (41O B) derives the
name from its perpetual motion-- oti aei thei peri ton
aera reon, aeitheer dikaios an kaloito), a material
substance of a more subtle kind than visible bodies, supposed
to exist in those parts of space which are apparently empty.
``The hypothesis of an aether has been maintained by different
speculators for very different reasons. To those who maintained
the existence of a plenum as a philosophical principle, nature's
abhorrence of a vacuum was a sufficient reason for imagining
an all-surrounding aether, even though every other argument
should be against it. To Descartes, who made extension the
sole essential property of matter, and matter a necessary
condition of extension, the bare existence of bodies apparently
at a distance was a proof of the existence of a continuous
medium between them. But besides these high metaphysical
necessities for a medium, there were more mundane uses to be
fulfilled by aethers. Aethers were invented for the planets
to swim in, to constitute electric atmospheres and magnetic
effluvia, to convey sensations from one part of our bodies to
another, and so on, till all space had been filled three or
four times over with aethers. It is only when we remember
the extensive and mischievous influence on science which
hypotheses about aethers used formerly to exercise, that
we can appreciate the horror of aethers which sober-minded
men had during the 18th century, and which, probably as a
sort of hereditary prejudice, descended even to John Stuart
Mill. The disciples of Newton maintained that in the fact
of the mutual gravitation of the heavenly bodies, according
to Newton's law, they had a complete quantitative account of
their motions; and they endeavoured to follow out the path
which Newton had opened up by investigating and measuring
the attractions and repulsions of electrified and magnetic
bodies, and the cohesive forces in the interior of bodies,
without attempting tdraccount for these forces. Newton himself,
however, endeavoured to account for gravitation by differences
of pressure in an aether; but he did not publish his theory,
`because he was not able from experiment and observation to
give a satisfactory account of this medium, and the manner of
its operation in producing the chief phenomena of nature.' On
the other hand, those who imagined aethers in order to explain
phenomena could not specify the nature of the motion of these
media, and could not prove that the media, as imagined by
them, would produce the effects they were meant to explain.
The only aether which has survived is that which was invented
by Huygens to explain the propagation of light. The evidence
for the existence of the luminiferous aether has accumulated
as additional phenomena of light and other radiations have
been discovered; and the properties of this medium, as deduced
from the phenomena of light, have been found to be precisely
those required to explain electromagnetic phenomena.''
This description, quoted from James Clerk Maxwell's article in
the 9th edition of the Encyclopaedia Britannica, represents
the historical position of the subject up till about 1860, when
Maxwell began those constructive speculations in electrical
theory, based on the influence of the physical views of Faraday
and Lord Kelvin, which have in their subsequent development largely
transformed theoretical physics into the science of the aether.
In the remainder of the article referred to, Maxwell reviews
the evidence for the necessity of an aether, from the fact
that light takes time to travel, while it cannot travel as a
substance, for if so two interfering lights could not mask
each other in the dark fringes (see INTERFERENCE OF LIGHT.)
Light is therefore an influence propagated as wave-motion, and
moreover by transverse undulations, for the reasons brought
out by Thomas Young and Augustin Fresnel; so that the aether
is a medium which possesses elasticity of a type analogous to
rigidity. It must be very different from ordinary matter as we
know it, for waves travelling in matter constitute sound, which
is propagated hundreds of thousands of times slower than light.
If we suppose that the aether differs from ordinary matter in
degree but not in kind, we can obtain some idea of its quality
from a knowledge of the velocity of radiation and of its
possible intensity near the sun, in a manner applied long ago
by Lord Kelvin (Trans. R. S. Edin. xxi. 1854). According
to modern measurements the solar radiation imparts almost 3
gramme-calories of energy per minute per square centimetre
at the distance of the earth, which is about 1.3X106 ergs
per sec. per cm.2 The energy in sunlight per cubic cm. just
outside the earth's atmosphere is therefore about 4X10-5
ergs; applying the law of inverse squares the value near the
sun's surface would be 1.8 ergs. Let E be the effective
elasticity of the aether; then E=rc2, where r is its
density, and c the velocity of light which is 3X1010
cm./sec. If x=A cosn (t-x/c) is the linear vibration,
the stress is E dx/dx; and the total energy, which is
twice the kinetic energy 1/2r(dx/dt)2dx, is 1/2rn2
A2 per cm., which is thus equal to 1.8 ergs as above. law
l=2pc/n, so that if A/l=k, we have 1/2r(2pck)2=
1.8, giving r=10-22k-2 and E=10-1k-2. Lord Kelvin
assumed as a superior limit of k, the ratio of amplitude
