PTOLEMY versus COPERNICUS.

103

reduced in scale) of his diagrams of the apparent paths ofMercury, Venus, and Mars, as they are seen from the Earth ,inasmuch as we think that the complication of the whole ofsuch a drawing as that in Fig . XXIV., makes it difficult torealize, so well as in a simpler figure, the actual character ofthe apparent curve described. We have also adapted thepaths shown to more recent dates.

' In Fig . XXVI. the apparent path of Mercury as seen from theEarth is drawn for a period of about cue year; and a somewhat

Ea*rth

Fig. XXVI.—Apparent path of Mercury as seen from the Earth during part ofthe years 1881 and 1882 .

careful consideration of the diagram may show that an intervalof about 116 days occurs between the beginning or the endingof two successive epochs of the planet’s retrogression, or betweenits being twice in the position of its nearest approach to theEarth .

In Fig. XXVII. the apparent path of Venus is represented forabout two years, its monthly places being marked by smalldots. This diagram also indicates that the• interval betweentwo successive nearest approaches to the Earth is very nearlyI?years (or about 584 days); one such approach taking place