LET. XI. AND VICISSITUDES OF "THE SEASONS. 189

round its axis, and the different places upon itssurface, will be carried through the light anddark hemispheres, and have the appearance ofa regular succession of day and night, in thesame manner as would take place upon the earth,by means of such a motion.

As the globe turns by the untwisting of thestring, move your hand slowly round the candle,according to the order of the letters abed ,keeping its center continually even with thewire circle, and you will perceive that the can-dle, being still perpendicular to the equator,will enlighten the globe from pole to pole,through the whole of its motion round thecircle j and that every place on the globe goesequally through the light and dark hemispheres,as it turns round by the untwisting of thestring, and has, therefore, a perpetual equinox,or an equal portion of day and night.

The globe turning in this manner, repre-sents the rotation of the earth upon its axis,and the motion of the globe round the candlethe earth’s annual revolution round the fun;and also shows, that if the axis of the earthhad no inclination to the plane of its orbit, allthe days and nights in the year would beequally long, and of course that there would beno variety of the seasons. This is exactly whatwould take place, if the earth moved in theequator instead of the ecliptic; but as that is not4. the