236 GEOGRAPIIY AND ASTRONOMY. which indeed are but the self same things on both the globes, though astronomers have happened to give them different names. Note,' The sun's utmost declination northward in our sum- mer is but 231 degrees ; and it is just so much southward in,- oar winter ; for then he returns again ; there the tropics areplaced which describe the path of the sun when farthest from the equator, at midsummer, or midwinter ; these two tropics art his parallels of declination on the longest and shortest day. While the sun gains 90 degrees on the ecliptic, (which is an oblique circle) in a quarter of a year, it gains hut 23i de- grees of direct distance from the equator measured on the me- ridian; this appears evident on the globe, and may be repre- sented thus in figure v. Let the semicircle Y P be the meridian of the northern hemisphere, the line T C h be the equator or the sun's path at Aries and Libra, the arch 23 ^ the ecliptic, the line T 23 0 the summer tropic, the line a e the sun's path when it enters Gemini and Leo, the line n s, the sun's path when it enters Taurus and Virgo;then it will appear that in moving from T to tj the sun gains 30 degrees in the ecliptic, in about a month, and at the saine time 12 degrees of declination, viz, from i to n. Then moving from jj to íI in a month more it gains 30 de- greeson the ecliptic, and 81 degrees of declination, viz. from u to a. Then again from Il to 23 in a month more it gains 30 degrees on the ecliptic, and but 3á degrees of declination, viz. from a to T. I might also shew the same difference between its declination and its motion on the ecliptic in its descent from 23 to Si , ny, and ^ . By drawing another scheme of the same kind below the line T C , we might represent the sun's descent towards the win- ter solstice, and its return again to the spring; and thereby shew the same differences between the sun's declination and its motion onthe eclipticin the winter half year as the present scheme shews in the summer half- year. Hereby it is evident how it comes to pass, that the sun's de- clination alters near half a degree every day just about the equinoxes; but it scarce alters so much in 10 or 12 days on each side of the solstices ; and this shews the reason why the length of days and nights changes so fast in March and September, and so exceeding slowly in Jane and December ; for according to the increase of the sun's declination in summer, its semidiurnal arce will be larger, and consequently it must be so much longer before it comes to its full height at noon, and it stays so much longer above the horizon before it sets. * The 'r diurnal are is that part of the circle or parallel of declinatiOn which is above the " horizon g" and the half of that part is caned the " diurnal are." ,
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