<£72 MAS K E 
MASK LOU'GH. See Lough, vol. xiii. 
MASKALE'VA, a town of Ruffia, in the government 
of Irkutfk, on the Angara: twenty-four miles north of 
Balaganfkoi. 
•M-AS'KELYNE (Nevil, D.D. F.R.S.), an eminent af- 
tronomer and mathematician, who filled the important of¬ 
fice of afironomer royal of England for the long period 
of forty-fix years, with the higheft credit to himfelf, and 
with great advantage as well as honour to his country. 
He was defcended from a good family long fettled in 
Wiltfhire, and was born in London Oft. 6, 173a. At 
nine years of age he was placed at Weftminfter fchool, 
where he continued until he was fifteen, and where he 
made a diltinguifhed progrefs in claffical learning. He 
alfo paid due attention to Engliflh literature; but mani- 
fefted a particular defire to underftand aftronomy, and the 
conftruftion of optical inftruments. This predileftion, 
it is faid, was confiderably increafed on feeing the memo¬ 
rable folar eclipfe of 174.8, exhibited through a large te- 
lefcope in a camera obfcura. It is remarkable that this 
eclipfe produced the fame effeft upon Lalande, the French 
afironomer, who was only three months older than Maf- 
kelyne. We may fay with truth that never was celefiial 
phenomenon more ufeful to the fcience than the eclipfe 
which furnifiied it with two afironomers fo Angularly dif- 
tinguifhed, though in different ways ; one of whom wrote 
a great deal, was long a profeffor, and formed a great 
number of pupils, but obferved very little; while the 
other wrote lefs, but has left us, in the colleftion of his 
Gbfervations, the greateft and moft valuable monument 
of the kind which exifts. 
From this period he applied himfelf with ardour to the 
ftudy of aftronomy and optics; but foon experienced the 
neceffity of laying a proper mathematical foundation for 
thofe fciences ; and he therefore turned his attention to 
the elements of geometry and algebra, which he learned 
in a few -months without the help of a mailer. Thus, like 
jnoft other eminent mathematicians, he may be considered, 
in a great meafure, as felf-taught; but, contrary to the 
ufual courfe of fuch Studies, his early turn for aftronomy 
led to his mathematical attainments. In 1749, he was 
entered at the univerfity of Cambridge ; he was firft 
placed at Catharine-hall, but foon after removed to Tri¬ 
nity-college, where he purfued his favourite ftudies with 
increafed luccefs ; and, on taking his firft degree, received 
diftinguifhed honours from the univerfity. He took his 
Several degrees at the following periods, A. B. in 1754, 
A. M. in 1757, B. D. in 1768, and D. D. in 1777. 
In 1755 he was ordained to the curacy of Barnet, where 
•lie officiated for fome time, and where he devoted moft 
of his leifure hours to the ftudy of praftical aftronomy. 
About this period he connefted himfelf with the great 
allronomer Bradley, for whom it appears he made different 
calculations of importance. In 1758 he became fellow 
of Trinity-college, Cambridge; and the next year he 
was elefted a fellow of the Royal Society. 
But it was'in the year 1761 that his real aftronomical 
career began, when he was chofen to go to the ifland of 
St. Helena, to obferve the tranlit of Venus over the fun’s 
difk. To render this voyage the more ufeful, he offered 
to the Royal Society to make obfervations on the paral¬ 
lax of Sirius. This beautiful ftar had been often ob¬ 
ferved by La Caille at the Cape of Good Hope. Dr. Maf- 
kelyne, from calculating thefe obfervations, thought he 
law proofs for the exijtence of a parallax of 4’5 / ', from 
which it would refult that Sirius is not fo far diftant from 
the earth as was commonly imagined. Clouds prevented 
the obfervation of the tranlit of Venus, which had given 
occafion to the voyage; but Mafkelyne, furnifiied with 
an excellent pendulum of Shelton, which had been regu¬ 
lated at Greenwich by Bradley, and which had been 
.tranfported with the greateft pcfiible care, determined 
tb« number of ofcillations which it made lefs in St. He¬ 
lena than at London, in order to deduce from that ob- 
LYNE. 
fervation the diminution of gravity. The fecondary ob- 
jeft of the voyage, the parallax of Sirius, likewife failed j 
but it produced an obfervation both curious and ufeful. 
To know if Sirius had a fenfible parallax, it was neceffary 
to have a more perfeft iuftrument than that of La Caille.; 
it was neceffary to obferve tile ftar in peculiar fituations. 
The firft of thefe requifites depended upon the artift; the 
fecond upon the aftronomer. The Royal Society had got 
a ftftor made on purpofe, which was only fiuilbed juft 
when the veflel failed, and could not be verified at Green¬ 
wich. What was the furprife of Mafkelyne when he 
found that this inftrument, dellined for the mod delicate 
refearches, gave from cue day to another differences of 
10", 20", and even 30", in the meafure of the fame an¬ 
gle ! In examining with care what could be the caufe 
of thefe fingular variations, he difeovered it without dif¬ 
ficulty, made himfelf certain of it by various proofs, and 
endeavoured to correft it, but could fucceed only imper- 
feftly. He reduced the error to 3 ,/ , which was far from 
being fufficient for the objeft that he had in view. This 
obliged him to renounce his fecond projeft. The refult, 
however, was an improvement in the conftruftion of 
thefe altronomical inftruments. 
But his voyage anfwered a more important purpofe, 
and one far more ufeful to his country, than that origi¬ 
nally intended ; it afforded him an opportunity of taking 
lunar obfervations, which were now' for the firft time made 
with effeft. This method of finding the longitude at fca 
had been long contemplated as a grand defideratum in 
navigation ; and plans and preparations had been made 
for the purpofe by Flamfteed, Newton, La Caille, Eu¬ 
ler, Halley, Bradley, Mayer, and others ; but the honour 
was referved for Dr. Mafkeiyne, to reduce their theories 
to fuccefsful praclice. This he was enabled to do by r 
means of Hadley’s quadrant recently invented; and alfo 
by Mayer’s Lunar Tables, for which a parliamentary re¬ 
ward of 3000I. was afterwards given, on Dr. Mafkelyne’s 
report of their correftnefs. During the voyage, both out¬ 
ward and homeward, he exercifed the officers on-board in 
taking lunar obfervations; and -taught them to clear the 
diltances from the effefts of parallax and refraftion, and 
thence to find the longitude within certain limits. While 
at the ifland, he made accurate obfervations on the tides, 
the variation of the compafs, and the comparative gravity 
of bodies there and at London. Pie alfo obferved the an¬ 
nual parallax of Sirius, and the horary parallaxes of the 
Moon. The chief re fit Its of thefe operations are inferted 
in the Philofophical Tranfaftions of the above period. 
Soon after his return from St. Helena, he publilhed his 
well-known work, entitled “The Britilh Mariner’s Guide,” 
which contained, among various new and praftical illuf- 
trations and articles in nautical aftronomy, rules and ex¬ 
amples for working the lunar obfervations ; but, in order 
to fiiorten and Amplify thefe laborious operations, other 
tables and calculations were dill wanted, which he after¬ 
wards fupplied by his Nautical Almanac and Requifite 
Tables. 
In 176311c made a voyage to Barbadoes, in order to ex¬ 
amine the goodnefs of Harrifon’s time-pieces. The report 
which he made at his return, though favourable in general 
to the celebrated artift whofe invention he had fubjefted 
to tiie moft fevere teft, was far from fatisfying Harrifon, 
who attacked him in a pamphlet. Mafkelyne wrote a re¬ 
ply to this attack. Naval men and philofophers took 
part with one fide or other, according to their ideas and 
their habits. M. de Fleurieu, particularly connefted with 
F. Berthoud, and devoted to the caufe of the time-pieces, 
forgot perhaps on this occafion his accuftomed modera- 
tion. It was a difpute between two ufeful methods, cal¬ 
culated to affift each other. Mafkelyne did not find the 
time-pieces fufficiently certain, nor fufficiently regular. 
Harrifon affirmed, not without reafon, that they were 
within the limits preferibed by the aft of parliament. He 
demanded the whole reward, which was afterwards given 
