li Mr. Pickering’s Eulogy on 
the place of the moving body at any time. This Appendix, as he 
observes in his advertisement to the volume, contains many impor- 
tant formulas and tables, which are useful to astronomers in making 
the computations just mentioned. Some of the Tables are new, 
and the others have been varied in their forms, to render them more 
simple in their uses and applications; none of them, he adds, have 
heretofore been published in this country ; and several of the for- 
mulas have been introduced into the calculations of modern astron- 
omy since the commencement of the first part of the original work. 
The Tables, as here given by Dr. Bowditch, are highly valued by 
astronomers for their convenience, beauty, and exactness. 
The theory of Comets concludes the inquiries of La Place relative 
to the matter and form, and the motions, of the various masses or 
bodies, which constitute the system of the world. There remains, 
however, another subject, intimately and essentially connected with 
those inquiries, —the subject of Light and the Theory of astro- 
nomical Refractions, — which the author then proceeds to examine. 
The motion of light in the mediums through which it passes, 
particularly in the atmosphere, is, as he observes, one of the most 
important objects of astronomy ; whether we consider it in relation 
to theory, or to its effect upon every astronomical observation. We 
view the heavenly bodies through a transparent medium, which 
by inflecting their rays changes their apparent position, and 
makes them appear in different places from those which they really 
occupy ; it is, therefore, important to determine the law of this 
inflection, so as to obtain the real situations of those bodies.* This 
investigation is accordingly pursued in the Tenth Book. The 
author adopts the Newtonian hypothesis of the emission of light ; 
which, however, has been much shaken by more recent observations 
tending to confirm the undulatory or wave theory. 
* Bowditch’s La Place. Vol. IV. p. 438. 
