SOURS RY An ee ee = he 
ok aaa aR aa ch aie ta oe MAD, 
James Graig Watson. 63 
discovery of a planet on the 20th of October, 1857, which, 
however, proved to have been observed by Luther a few days 
before, and has been named Aglaia. His observations of 
Donati’s comet, in 1858, possess a standard value, and his com- 
putation of the orbit is recognized as authoritative. The 
interest awakened by this comet prompted to the preparation 
of “A Popular Treatise on Comets,” published early in 1860. 
In 1860, Dr. Briinnow resumed the directorship of the obser- 
vatory, and young Watson was assigned to the chair of Physics 
in the University, which he retained for three years, when, on 
the final retirement of Dr. Briinnow, Watson was made Professor 
of Astronomy and Director of the observatory—a position which 
he held and honored for sixteen years. Scarcely had he been 
clothed with full control of the instraments when he resumed 
his remarkable career of discovery. There seemed almost a 
magic in his powers. Unrecognized celestial objects seemed 
to crowd spontaneously upon his notice. On September 14, 
1863, he made his first independent planetary discovery. This 
was Hurynome. On January 9, 1864, he discovered the comet 
since known as 1868, VI, which Respighi, as it proved, had 
already noted. On the 9th of October, 1865, he discovered a 
planet which also proved to have been announced by Peters, 
and has since been named Jo. He discovered Minerva, August 
24, and Aurora, September 6, 1867. During 1868, he added 
no less than six minor plants to the solar system, furnishing 
the only instance in which the list of planetary discoverers pre- 
sents the same name four times in immediate succession. 
Meantime he was engaged upon a work which might well 
have engrossed all. his powers, and must have quite exceeded 
the abilities of any but a gifted mathematical genius. It was 
no less than a complete digest of the results and methods of all 
the great writers on theoretical astronomy, and an independent 
_ development of the great principles of the science. ‘ Havin 
carefully read the works of the great masters,” he says in his 
preface, “my plan was to prepare a complete work on the 
subject, commencing with the fundamental principles of 
dynamics, and systematically treating, from one point of view, 
all the problems presented.” is broad plan, conceived 
y @ young man of twenty-eight, and completed when twenty- 
nine, was executed with ability so commanding, that the work, 
on its appearance, in 1869, was immediately accepted as an 
authoritative exposition of the higher principles and processes 
of dynamical astronomy, and was made a text-book at Leipzig, 
at Paris and at Greenwich. The same year he was sent by the 
eneral Government on an expedition to observe the solar 
eclipse at Mt. Pleasant, Iowa; and in 1870, to Carlentini, 
Sicily, for a similar purpose. In 1874 he was appointed to the 
