A compendium of astronomy: being a concise description of the most interesting phenomena of the heavens (1849)

Record Details:

Something wrong or inaccurate about this page? Let us Know!

Thanks for helping us continually improve the quality of the Lantern search engine for all of our users! We have millions of scanned pages, so user reports are incredibly helpful for us to identify places where we can improve and update the metadata.

Please describe the issue below, and click "Submit" to send your comments to our team! If you'd prefer, you can also send us an email to mhdl@commarts.wisc.edu with your comments.




We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.

Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.

31 it on to l , the attractive force of the Sun will only draw it out of the straight line by the amount g j, or l in ; instead of the amount g o, or l n, which would be re- quired to keep it at the same distance from the Sun ; so that instead of moving in a circular path to n, its distance will increase again, and it will traverse the elliptical path rn, a continuation of which, produced by the same joint action of the two forces, will carry it on to A, with a constantly diminishing rate of movement. By the time it reaches A, the projectile force is reduced so far as to be again overpowered by the attractive; so that the distance begins to diminish, and the motion to he accelerated as before. DIAGRAM XXV. This figure explains what is meant by the parallax of the heavenly bodies, on which is founded our estimate of their distances from us and from each other. This term is used to designate the difference in their apparent places, consequent upon the different positions of the observer. Every one must have noticed that, when walking or riding through a country, there is a continual change in the aspect of the scene, arising from the change in the direction under which we view it ; the apparent position of the nearer objects being much more altered than that of the distant ones. The same is true of the heavenly bodies; the apparent places of the Sun, Moon, and Planets, among the fixed stars, being different according to the position of the observer on the Earth’s surface. Thus to an obsever at A, the bodies B and D will seem to be in the same line, and their apparent place among the fixed stars will be at G. But to an observer situated at the centre of the Earth, or on the point A' of its surface, the apparent place of the body B will be at E, and that of the body 1) at F; this angular movement, which is termed parallax, being greater for the nearer than for the more distant body. In like manner, the bodies H and P, which are seen