This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1799 Excerpt: ...As telescopes were in use at that time, it is probable that each might make the discovery. Admitting these spots to adhere to the sun's body, the reasons sor which we shall afterwards give, we proceed to show, how the time of it's rotation may be found. 238. M. Cass1n1 determined the time of rotation, from observing ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1799 Excerpt: ...As telescopes were in use at that time, it is probable that each might make the discovery. Admitting these spots to adhere to the sun's body, the reasons sor which we shall afterwards give, we proceed to show, how the time of it's rotation may be found. 238. M. Cass1n1 determined the time of rotation, from observing the time in which a spot returns to the fame situation upon the disc, or to the circle of latitude passing through the earth. Let t be that interval of time, and let m be equal to the true motion of the earth in that time, and n equal to it's mean motion; then 36o0 + -: 36o0+-:: /: the time of return if the motion had been uniform, and this, from a great number of observations he determines to be 27/. 12AE. ao'; now the mean motion of the earth m that time is 270. 7'. 8"; hence, 36o0 + 2 70. 7'. 8" 3600:: 27..12AE. 20' 2$d. 14AE. 8' the time of rotation Elem. de' AJiron. pag. 104 239. When the earth is in the nodes of the sun's equator, it being then in it's plane, the spots appear to describe straight lines; this happens about the beginning of June and December. As the earth recedes srom the nodes, the path of a spot grows more and more elliptical, till the earth gets 900 from the nodes, M 2 which 1 which happens about the beginning of September and March, at which time the ellipse has it's minor axis the greatest, and is then to the major axis, as the fine of the inclination of the solar equator to radius. 240. There has been a great difference of opinions respecting the nature of the solar spots. Sche1ner supposed them to be solid bodies revolving about the sun, very near to it; but as they are as long visible as they are invisible, this cannot be the cafe. Moreover, we have a physical argument against this h
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