22 G. H. KNIBBS. 



At a few of the developments of its higher applications, we may 

 be allowed to briefly glance ; and first in regard to astronomy. 

 Kepler's work therein has already been noticed. The illustrious 

 Bessel [1784 - 1846] who sacrificed the prospect of affluence 'for 

 poverty and the stars,' practically recast the science, introducing 

 into it rigorous methods, and greatly improving the value of its 

 constants, thereby making possible the accurate prediction of the 

 positions of celestial objects. He alone appreciated the work of 

 our own astronomer Bradley at its true worth, and utilized it. 

 Geodesy — the connection of which with astronomy is very intimate 

 — he founded as a science. For the development of the lunar 

 theory we are indebted to Hansen [1795-1874], and to his 

 indefatigable computations of extensive lunar tables, the basis of 

 the positions of the moon on which the navigator is so dependent 

 for his safety. Poisson [1781-1840] discussed the secular 

 inequalities of the mean motions of the planets : Airy [1801 - 

 1892] the planetary and lunar theories and that of the tides, pre- 

 viously treated by Laplace. Leverrier [1811-1877] and J. C. 

 Adams [1819 - 1892] shared the honour of discovering Neptune 

 by studying the unexplained deviations of the place of Uranus. 

 Delaunay [1816-1872] completed the explanation of the secular 

 acceleration of the moon's mean motion, which Adams had 

 shewn was defective. Newcomb [born 1835] investigated the 

 imperfections of Hansen's tables and also greatly improved the 

 determination of lunar places, and therefore of longitude by lunar 

 methods. Adams and G. H. Darwin [born 1845] have developed 

 a scheme of tidal analysis ; Darwin himself studying also tidal 

 friction. Quite a number of workers have attacked the problem 

 of n bodies, which is really the problem of astronomy; but Bruns 

 has shewn that no advance may be expected by algebraic integrals, 

 and that if a solution be possible, we must look to the modern 

 theory of functions for it. 



Further improvement in the selection of a fixed point of refer- 

 ence for celestial positions, and in the determination of mean 

 places, depend upon the ascertainment of the sun's path in space. 



