Physics, the first principles of which all bodies are composed. These, it has been supposed, are few in number, unchangeable in their nature, and, by their multiform combinations, produce that endless variety of objects which we observe in the works of creation.

Astronomy, are those principles deduced from astronomical observations and calculations; and those fundamental numbers which are employed in the construction of tables of the planetary motions. Thus, the elements of the theory of the sun, or rather of the earth, are its mean motion and eccentricity, and the motion of the aphelia. The elements of the theory of the moon are its mean motion, that of its node and apogee, its eccentricity, the inclination of its orbit to the plane of the ecliptic, and so on.