Royal Society. — 155 
of its application, and the economy of time resulting from its use, the 
employment of the level and plumb-line may be wholly superseded. 
John Brinkley, Lord Bishop of Cloyne, commenced his scientific 
career, while Andrews Professor of Astronomy in the University of 
Dublin, by a mathematical paper published in the Phil. Trans. for 
1807, containing an investigation of the general term of an important 
series in the inverse method of finite differences. In 1810 Dr. Mas- 
kelyne, then Astronomer Royal, announced to the Society by the 
communication of a letter from Dr. Brinkley, the supposed discovery 
by the latter of the annual parallax of « Lyre, which he was confident 
exceeds 2. In 1818 he reported having met with apparent motions 
in several of the fixed stars which he could explain only by referring 
them to parallax. Among these « Aquile exhibited the greatest 
change of place. The observations made at the Greenwich obser- 
yatory not being in accordance with those made at Dublin, Dr. 
Brinkley, in a subsequent paper published in the Phil. Trans. for 
1821, institutes a new series of observations with a view to discover 
the source of this discordance. . In conclusion he states his inability 
to discover any explanation of this difference, or to obtain any result 
opposed to his former conclusions. He remarks, however, that the 
discrepancies between his observations and those made at Greenwich 
may by some be considered as showing the great precision of modern 
observations, since the whole extent of the absolute difference is 
only one second. In the last paper on this important subject, which 
was published in the Phil. Trans. for 1824, Dr. Brinkley endeavours 
to form a correct estimate of the absolute and relative degrees of 
accuracy of the instruments at Dublin and at Greenwich. He first 
considers the difference of parallax between y Draconis and a Lyre, 
and secondly the absolute parallax of a Lyre. 
Four other papers by the same author are also contained in the 
Philosophical Transactions: the first in 1819, giving the results of 
observations made at the observatory of Trinity College, Dublin, for 
determining the obliquity of the ecliptic, and the maximum of the 
aberration of light; the second, published in 1822, containing the 
investigation of the elements of a comet observed by Captain Basil 
Hall ; the third published in 1824, on the North Polar distances of 
the principal fixed stars ; and the last, which appeared in 1826, com- 
municating the results of the application of Capt. Kater’s floating 
collimator to the astronomical circle at the observatory of Trinity 
College, Dublin. He regards the results of these observations as 
highly favourable to the principle of the collimator, which he con- 
siders as a new astronomical power, and as even belonging to a more 
advanced era of practical astronomy than the present. 
Mr. Edward ‘Troughton is the author of a paper in the Phil. Trans. 
for 1809, entitled “‘ An Account of a method of dividing Astronomical 
and other instruments by ocular inspection; in which the usual tools 
for graduating are not employed; the whole operation being so con- 
trived, that no error can occur but what is chargeable to vision when 
assisted by the best optical means of viewing and measuring minute 
quantities.” The intrinsic excellence of Mr. Troughton’s method, 
$2 
