SECTION XX. 803 the sun than the other part of it which the earth traces in our summer half-year, (i. e. from spring to autumn.) And as it is nearer to the sun, so consequently it is the shorter or lesser half, if I may so express it. The very figure shows it plainly. Note, By our winter and our summer I mean those seasons as they respect us in Europe, and in these northern parts of the globe. 4. Thence it follows that the sun appears to finish its winter half-year from September 23d to March 20th, i. e. from = by 1/5' to T sooner by 7 orS days than it does the summer half-year, i. e. from T by 25 to -, orfrom March20th to September 23d, which is proved thus : When the earth is at t, the sun appears at 2 and it is midsummer. When the earth is at e the sun ap- pears at s and it is autumn. When the earth is at o the sun appears at '/3 and it is midwinter. And when the earth is at a the sun appears at T and it is spring. Thus the sun appears to pass through those signs which are just opposite to those which the earth passes. Now as the earth is longer in going through the arch a t e, from to T than it is going through the arch e o a, from to =0-, so consequently the sun appears to pass through the opposite signs front aries to libra, slower than he does from libra to aries. This is proved also plainly by the computation of days. After the sun enters aries on March 20th, that month bath 11 days, and after the sun enters Libra on September 23d, that month Math 8 days. Now let us compute. March 11 T September 8 .AJpril 30 October 31 May 31 November 30 June 30 Days December 31 Days July 31 January 31 August 31 February 28 September 22 March 20 T Summer 1$0 Days Winter 179 Days 5. Agreeably hereto it is found that in the winter months (chiefly from the latter end of October to the middle of March) the sun appears to move something more than one degree in a day : But in the summer months (chiefly from the middle of March to the latter end of October) the sun appears, to move something less than one degree in a'day. This is one reason why a goodpendulum clock measures time more justly than the sun : And it is this irregularity of the sun's measuring time that makes the tables of equation of time necessary. 0. Aud thence arises a sensible inequality between the times
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