378 Chauvenet’s Spherical and Practical Astronomy. 
Art, XXXII.—Chauvenet’s Manual of Spherical and Practical 
Astronomy.’ 
[Szeconp Norice.] 
THE publication of this work opens a new era for the student 
of astronomical science. Henceforth, the study of spherical and 
‘soleaees astronomy is a very different thing from what it 
en with all the aids previously existing in the English, French 
and German languages. That these assertions may not seem 
exaggerated, we propose to give a somewhat detailed account of 
those parts of the work which are original with the author, and 
which we think of sufficient importance to establish the truth 
of our assertions. 
Chapter I, on Spherical and Rectangular Coérdinates, initiates 
the student into the method of applying spherical trigonometry 
to astronomical problems, in the most general manner. The 
expressions for the rectangular codrdinates of a point in space, 
in terms of the distance of the point from the origin and of the 
spherical codrdinates, are deduced in a new and extremely sim- 
ple way. 
Chapter II, on Time and the use of the Ephemeris, is 
unusually complete on various minor points which are apt to 
embarrass beginners—such as the conversion of mean or apparent 
solar time into sidereal time; the deduction of local time from 
the given hour angle of any celestial body, and the inverse 
problems ; the management of interpolation formulas in consult- 
ing the ephemeris, ete.—with all of which the young astronomer 
must be perfectly familiar before he can proceed. 
Chapter IIT, on the Figure of the Earth, does not treat the 
methods of determining the earth’s figure, which is left to 
geodesy, but gives the geodetic formulas, with their demonstra- 
tion, which are necessary to the astronomer in reducing observa 
tions to the centre of the earth. Bessel’s dimensions of the 
terrestrial spheroid are adopted. The author has not forgotten 
to notice the “ abnormal deviations of the plumb line,” which 
render it necessary to distinguish between the astronomical and 
the geodetic latitude or longitude ofa point on the earth’s sur- 
face ; deviations which were first pointed out and also accurately 
determined by our own admirable Coast Survey. Now that 
existence of such deviations is established, and the method 
of eliminating them pointed ont, it is certainly desirable that a 
new measurement of the earth’s dimensions should be entered 
, Upon by the leading nations of the world. It can hardly be 
_ doubted that the earth will be found to differ sensibly froman 
__? A Manual of Spherical and Practical Astronomy. By Witutam Caavvener, LD, 
Chaves of Watington Unie, St Louis Mo.” Published by J.B Lippine 
Pie cae ee Oe ge ee ae 2 nt ole ee. 
