14 ^4 Comprehensive View

arising from the earth’s annual motion inits orbit, is as follows : In fig. 7. 8 repre-sents the fun, T, the earth in its orbit T t,and R Q__the concave sphere of the fixedstars. Whilst the earth is moving in its orbitfrom T to t, the fun seems to move thro’the starry arch from Q^jo R, which mea-sures the angle R S Q, equal to the angleT S t, so that the celerity of the apparentmotion of the sun depends upon the ce-lerity of the angular motion of the earth,with respect to the center of the sun. Ina whole revolution of the earth, the sunalso seems to run through a whole circle.

35. The earth moves round the funbetween the orbits of Venus and Mars,in 365 days, 5 hours, 49 minutes. Besidesthis annual motion, it turns round its ownaxis in 24 solar hours; its axis is constantlyinclined in an angle of 66f degrees to theplane of the earth’s orbit, or the ecliptic,and keeps continually parallel to itself inevery part of its revolution.

In fig. 8. S represents the fun, A BCDthe orbit of the earth; in the periphery ofwhich, the center of the earth is carriedround the fun, according to the order of

the