RECENT PROGRESS IN THEORETICAL ASTRONOMY. 19 
Professor Ormond Stone, director of the Leander McCor¬ 
mick Observatory, has published a paper on Hyperion which 
sets forth clearly the principal inequality of its motion, and 
is of high importance to the future student of this remark¬ 
able object. It was presented to the Third Conference of 
Astronomers and Astrophysicists, and a short abstract of its 
principal points may be found in a recent number of Science. 
In the gravitational theory of the sun’s heat, advances on the 
theory of Helmholtz have been made by Professor T. J. J. 
See, of the Naval Observatory, who has determined the effect 
of heterogeneity in increasing the sun’s age 1 2 . His researches 
on the theory of gaseous bodies have thrown additional light 
on the classification of the stars and disclosed important 
data respecting the original condition of the solar system, 
which now appears to have been at a very low temperature 
when the planets were formed. It also appears certain that 
the planets never attained high temperatures, and that the 
diffuse nebulae are quite cold.* In the line of double stars 
the activity of the past year has kept pace with the progress 
made in this branch in former years. Several new orbits 
and many measures of double stars have appeared, and lastly 
a very important Reference Catalogue of all the Double Stars 
of the Southern Hemisphere, by Mr. R. T. A. Innes, of the 
Royal Observatory, Cape of Good Hope. 
Professor S. J. Brown, of the Naval Observatory, has con¬ 
cluded his careful and elegant researches on the orbit of the 
satellite of Neptune. He obtains an extremely accurate set 
of elements, and, by means of the motion of the orbit plane 
during the past quarter of a century, is enabled, on certain 
hypotheses, to evaluate the oblateness of the planet and the 
obliquity of the planet’s equator to the plane of the satellite’s 
orbit. 
The oblateness comes out about 
1 
102 . 2 ’ 
and the ob¬ 
liquity eighteen degrees. The period of revolution of the pole 
1 Astron. Nachr., No. 3586, July, 1899. 
2 Transactions of the Academy of Sciences of St. Louis, vol. X, No. 1, 
February 5, 1900. 
