16 ABE 
ABERLADY, a village in Eaft Lothian.— Aberlem- 
no, in the (hire of Angus.— Aberley, Aburley, or 
Abbotsley, Worcefterfhire.— Aberlour, in the thire 
of Elgin. 
ABERNETHY (John), an eminent diiTenting minifter, 
born at Colraine on the 19thof OCtober, i,6So. He ftudied 
at the univerlity of, Glafgow, till he took the degree of 
mailer of arts; and, in 1708, he was chofen minifter of a 
diffentirtg congregation at Antrim, where he continued 
above twenty years. About the time of the Bangorian 
controverfy, a diflention arofe among his brethren in the 
miniftry&t Belfaft, on the fubjeCt of fubfcription to the 
Weftminfter confellion; in which he became a leader on 
the negative fide, and incurred the cenfure of a general 
fynod. Being in confequence deferted by the greateft part 
of his congregation, he accepted an invitation to fettle in 
Dublin, where his preaching was much admired. He was 
diftingujflied by his candid, free, and generous, fentiments; 
and died of the gout, December 1740, in the 60th year of his 
age. He publifhed a volume of Sermons on the Divine 
Attributes; after his death a fecond volume was publifhed 
by his friends; and thefe were fucceeded by four other 
volumes on different fubje&s: all of which have been 
greatly admired. 
Abernethy, a town on the river Spey, in Murray- 
flf.re, near which was eredted a famous monument, called 
Macduff’s crofs; where if any, within the ninth degree to 
Macduff, fled, for manflaughter, he was pardoned on 
paying a few heads of cattle, by way of fine. 
Abernethy, a town in Strathern, a diftriCt of Perth- 
fhire, in Scotland. It is feated on the river Tay, a little 
above the mouth of the Erne. It is faid to have been the 
feat of the Piftifh kings; and was afterwards the fee of an 
archbifhop, lince transferred to St. Andrew’s. It is now 
greatly decayed. 
ABERRANCE, or Aberrancy, f. [from aberro, 
Lat. to wander from the right way. ] A deviation from the 
right way; an error; amiftake; a falfe opinion.—Could a 
man be compofed to fuch an advantage of conftitution, 
that it mould not at all adulterate the images of his mind; 
yet this fecond nature would alter the crafts of hisunder- 
ftanding, and render it as obnoxious to aberrances as now. 
Glanville. 
ABERRANT, adj. [from abcrrans, Lat.] Deviating, 
wandering from the right or known way. 
ABERRATION, J. \_abcrr-atio, Lat.] The act of devi¬ 
ating from the common or accuftomed track. 
Aberration, in aftronomy, an apparent motion of 
the celeftial bodies, obferved in the laft century by M. Pi¬ 
card, Dr. Hook, Flamltead, and others; but explained 
only of late years, by the ingenious Dr. Bradley, who, for 
the purpofe of difcovering the true caufes of this remark¬ 
able phenomenon, ereCted an apparatus for the zenith of 
Kew, and another for that of Wanftead, in order to ob- 
ferve more accurately fuch ftars as he judged likely to throw 
fome light upon the fubjecl. 
On the 3d of December 1725, the bright ftar in the head 
of Draco, marked 7 by Bayer, was for the firft time ob¬ 
ferved, as it palled near the zenith, and its fituafion care¬ 
fully taken with the inftrument; and, about the beginning 
of March following, the ftar was found to be 20" more 
foutherly than at the time of the firft obfervation. It 
now feemed to have arrived at its utmoft limit fouthward ; 
for in feveral trials, made by Dr. Bradley about this time, 
no fenftble difference was obferved in its fttuation. By the 
middle of April, however, it appeared to be returning 
back again towards the north; and, about the beginning 
of June, it paffed at the fame diftance from the zenith as 
it had done in December, when it was firft obferved. 
From the quick alteration in the declination of the ftar 
at this time, increafing about one fecond in three days, it 
was conjectured that it would now proceed northward, as 
it had before gone fouthward, of its prefent fttuation; 
and it happened accordingly; for the ftar continued to 
move northward till September following, when it became 
ABE 
ftationary again ; being then near 20" more northerly than 
in June, and upwards of 39"more northerly than it had 
been in March. From September the ftar again returned 
towards the Youth, till, in December, it arrived at the 
fame fttuation in which it had been obferved twelve months 
before, allowing for the difference of declination on ac¬ 
count of the precellion of the equinox. 
After continuing thefe obfervations a few months longer, 
Dr. Bradley difeovered What he then apprehended to be a 
general law obferved by all the ftars, namely, that each 
of them became ftationary, or was fartheft north or fouth, 
when it paffed over his zenith at fix of the clock, either in 
the evening or morning. He perceived alfo that whatever 
fttuation the ftars were in, with refpeft to the cardinal 
points of the ecliptic, the apparent motion of every one 
of them tended the fame way, wftdn they paffed his in¬ 
ftrument about the fame hour of the day or night; for 
they all moved fouthward when they paffed in the day, 
and northward when in the night; fo that each of them 
was fartheft north, when it came in the evening about fix 
of the clock, and fartheft fouth when it came about fix in 
the morning. , 
After two years had been employed in thefe obferva¬ 
tions, he at laft difeovered, through an amazing fagacity, 
that this apparent motion of the ftars was only a deception 
on the optic nerve, occafioned by the progreffive motion 
of light, and the earth’s annual motion in her orbit: for 
he perceived', that if light were propagated in time, the 
apparent place of a . fixed objeCt would not be the fame 
when the eye is at reft, as when it is moving in any other 
direction but that of the line pafling through the objeCt and 
the eye; and that, when the eye Amoving In different di¬ 
rections, the apparent place of the objedt would be different. 
M. de Maupertuis, in his Elements of Geography, gives 
a familiar and ingenious idea of the aberration, in this 
manner: “ It is juft the fame, (fays he,) concerning ,the 
diredtion in which a gun mult be pointed to ftrike a bird 
in its flight; inftead of pointing it ftraight to the bird, the 
fowler will point a little before it, in the path of its flight, 
and that fo much the more as the flight of the bird is more 
2‘apid, with refpeCt to the flight of the. fliot.” In this 
way of confidering the matter, the flight of the bird re- 
prefents the motion of the earth, and the flight of the fliot 
reprefents the motion of the rays of light. 
M. Clairaut too, in his Memoires of the Academy of 
Sciences for the year 1746, illuftrates this effeCt in a fami¬ 
liar way, by fuppofing drops of rain to fall rapidly and 
quickly after each other from a cloud, under which a per- 
fpn moves with a very narrow tube; in which cafe it is 
evident that the tube mult have a certain inclination, in 
order that a drop which enters at the top may fall freely 
through the axis of the tube, without touching the fides 
of it ; which inclination mud be more dr lefs, according 
to the velocity of the drops in refpeft to that of the tube: 
then the angle made by the direction of the tube and of 
the falling drops, is the aberration arifing from the com¬ 
bination of thole two motions.—This difeovery is certain¬ 
ly one of the brighteft of the prefent age. 
Aberration of the Planets, is equal to the geocentric 
motion of the planet, the fpace it appears to move as feen 
from the earth, during the time that light employs in paf- 
fing from the planet to the earth. Thus in the fun, the 
aberration in longitude is conftantly 20 fee. that being the 
fpace moved by the fun, or, which is the‘fame thing, by 
the earth, in the time of 8 min. 7 fee. which is the time 
in which light paffes from the fun to the earth. In like 
manner, knowing the diftance of any planet from the 
earth, by. proportion it will be, as the diftance of the fun 
is to the diftance of the planet, fo is 8 min. 7 fee. to the 
time of light pafling from the planet to the earth: then 
computjng the planet’s geocentric motion in this time, 
that will be the aberration of the planet, whether it be in 
longitude, latitude, right afeenfion, or declination. 
Aberration, in optics, the deviation or difperfion of 
the rays of light when reflected by a fpeculum, or re¬ 
traced 
