distance of the objects from the eye before they were removed.
That is to say in the object t and the object e the proportion of their distances from the eye a is quintuple. I remove each from its place and set it farther from the eye by one of the 5 parts into which the proposition is divided. Hence it happens that the nearest to the eye has doubled the distance and according to the last proposition but one of this, is diminished by the half of its whole size; and the body e, by the same motion, is diminished 1/5 of its whole size. Therefore, by that same last proposition but one, that which is said in this last proposition is true; and this I say of the motions of the celestial bodies which are more distant by 3500 miles when setting than when overhead, and yet do not increase or diminish in any sensible degree.
871.
a b is the aperture through which the sun passes, and if you could measure the size of the solar rays at n m , you could accurately trace the real lines of the convergence of the solar rays, the mirror being at a b , and then show the reflected rays at equal angles to n m ; but, as you want to have them at n m , take them at the. inner side of the aperture at cd, where they maybe measured at the spot where the solar rays fall. Then place your mirror at the distance a b , making the rays d b , c a fall and then be reflected at equal angles