Lectures on astronomical theories . from the earth ; and let e. represent a fifth star interme-diate in situation between the others as shown in thefigure. Viewed from the earth, the five stars may presentthe appearance of an equidistant one under theother, with equal inten^als. 10 PARALLAX. Now if the reader apprehends the general principle ofParallax, he will be able to consider with me a case whichhas been hitherto, I believe, somewhat overlooked, evenin advanced treatises on theoretical astronomy. Let. be a space on a road, say 100 feet in length, andlet d. be a tree at a hun
Lectures on astronomical theories . from the earth ; and let e. represent a fifth star interme-diate in situation between the others as shown in thefigure. Viewed from the earth, the five stars may presentthe appearance of an equidistant one under theother, with equal inten^als. 10 PARALLAX. Now if the reader apprehends the general principle ofParallax, he will be able to consider with me a case whichhas been hitherto, I believe, somewhat overlooked, evenin advanced treatises on theoretical astronomy. Let. be a space on a road, say 100 feet in length, andlet d. be a tree at a hundred yards distance, close against ahigh wall W. W. If an observer walk from A. to B., look-ing at the tree against the wall; the tree will not furnishany , and if there be any mark behind or abovethe tree by which to identify its place on the wall, thatplace will be seen to remain the same whether the ob-server be at A. or at B., or any where between , now, take away the wall, and refer the first tree to asecond tree behind it, at a distance of 200 yards from theroad; let the observer again walk the distance ob-serving the first tree with reference to the second, and it(the first tree) will be found to furnish a very conside-rable and notable amount of parallax. If we now, bearing this case in mind, contemplate thecelestial sphere, we feel the necessity of considering thenature of that which we are accustomed to call the con-cave surface of the heavens, or of the celestial
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Keywords: ., bookcentury18, bookdecade1870, booksubjectastronomy, bookyear1876
