113
entire loop of the apparent orbit be completed. The additionaltime involved, proves, in thfe case of Jupiter , to be 33 days,and in the very similar case of Saturn, 13 days.
IV e have thus far refrained from any special reference tothe case of Mars , because it happens that the circumstancesinvolved, and the figure necessary to explain them, are much
Fig. XXXII.—Showing, by means of a Cycle and Epicycle, that Mars takes more thantwo years to describe one complete loop of its apparent orbit.
more complicated. We will now, however, put before ourreaders a drawing, which may perhaps suffice to show, that, ifMars be supposed to revolve once round its epicycle in a year,while the centre of the epicycle rotates round the Earth in687 days, the planet must perform more than two completerevolutions in the epicycle, and occupy more than two years in
8