[4] Bonnycastle's Astronomy.
[5] Library of Useful Knowledge: History of Astronomy, page 95.
[6] Sir J. Herschel.
[7]A tangent is a straight line touching a circle, as A D, in Fig. 28
[8] Dick's 'Celestial Scenery,' Chapter IV
[9] Dick's 'Celestial Scenery.'
"As when the moon, refulgent lamp of night, O'er heaven's clear azure sheds her sacred light, When not a breath disturbs the deep serene, And not a cloud o'ercasts the solemn scene, Around her throne the vivid planets roll, And stars unnumbered gild the glowing pole; O'er the dark trees a yellower verdure shed, And tip with silver every mountain's head; Then shine the vales, the rocks in prospect rise, A flood of glory bursts from all the skies; The conscious swains, rejoicing in the sight, Eye the blue vault, and bless the useful light."
Pope's Homer.
[11]The exact longitude of the City Hall, in the city of New York, is 4h. 56m. 33.5s.