21 % OF THE EQUATION OF TIME.

from t to A; whilst those of the second qua-drant, from x to -o-, would come so much laterto it. In the third quadrant the same thingswould take place as in the first, and in thefourth as in the second ; and where the eclipticis most oblique, about Aries and Libra, it isevident, that the difference would be greatest;and least about Cancer and Capricorn, where theobliquity is least.

Having explained one cause of the differenceof time, as shewn by a well regulated clock anda true sun-dial, I shall now proceed to the other,and endeavour to make that equally easy andintelligible. The obliquity of the ecliptic is notthe only cause of an inequality in the length ofdays, but this inequality arises also from theunequal motion of the fun himself. This mo-tion is slowest in summer, when the sun is far-thest from the earth, and swiftest in winter,when he is nearest to it; as is evident from hisstaying longer in the northern half of the eclip-tic than in the southern half, by about eightdays : and therefore, although there were noobliquity of the ecliptic, the motion of the funwould not be a true and exact measure of time.For this motion sometimes exceeds a degree mtwenty-four hours, and is sometimes less; and,consequently, when it is slowest, any particularmeridian will come round sooner to him thanwhen it is swiftest; so that the days, from