Astronomy. 145 
Iv. ASTRONOMY. 
1, Theoretical Astronomy relating to the motions of the Heavenly 
Bodies revolving around the Sun in accordance with the law of 
&e.; by James C. Watson, 8°, pp. , 
1868. Philad., J. B. apes & Co. London, Trubner & Co.— 
. ? 
direct computation of orbits. The third chapter is devoted to 
parabolic orbits, and the methods of computing them from three 
complete observations. As the six coérdinates from three complete 
observations are more than sufficient to determine the five elements 
of a parabolic orbit, a method for correcting the elements by the 
variation of one of the extreme geocentric 
elements from three complete observations. The fifth chapter 
considers the same problem where four observations are given, of 
” b 
and the inclination of the plane of the orbit, for correcting by the 
penation of one geocentric distance, the formulz expressing relations 
pctween two places in the orbit, and those for correcting the orbit 
