SECTION XX. 305 It is not possible to form all this irregular variety of tim es when the sun enters the several signs into any memorial lines or rhymes with any exactness and perspicuity ; and therefore I have omitted the attempt. Such a short table as this may be always carried about by any person who deals frequently in such opera- tions end enquiries. But to give an example of the practice. Suppose it be en- quired, what is the sun's place, April 25th ? I find the sun just entered into taurus 8 April the 20th, then I reckon it is in the 5th degree of rj April 25th, which added to the whole 30- de- grees of aries, shews the sun to be 35 degrees from the equinoc- tial point r on the 25th of April. If the 29th of November we enquire the sun's place, we must consider the sun is just entered j the 22d of November : Therefore on the 29th it is about 7 degrees in / , which added to 3i/degrees of ,II, and 30 degrees of = shews the sun on the 29th of November, to be about 67 degrees from the autumnal equinox or =. Thus by adding or substracting as the case requires, you may find the sun's place any day in the year : And thence you may compute its distance from the nearest equinoctial point, which is of chief use in operations by the analemma. Problem XXI. " The day of the month being given, to draw the parallel of declination for that day without any tables or scales of the sun's declination." This may be done two ways. The first way is by consider- ing the sun's place in the ecliptic, as May 6th, it is 461 degrees from the equinox northward. Therefore in figuré xxiv. after you have drawn H z o the meridian, E c the equator, set up23 degrees the sun's greatest declination from E to ns ; draw sr c to represent the ecliptic ; then take 461 degrees from a line or scale of sines and set itfrom c the equinoctial point to it in the ecliptic ; through the point x, draw n a parallel to E c the equator. Thus D x represents the sun's path that day, and shews the declination to be a » or 16f. Note, If you have never a scaleof sines at hand, then take the chord or the arch of 481' degrees, set it up in the limb from H to a, set one foot of the compasses in G, and take the nearest distance to the line n o or diameter, and that extent is the sine of 461 degrees. The other way of drawing a parallel of declination, is by seeking what is the meridian altitude for the 6th of May, and you will find it to be 55 degrees. Set up therefore the arch of 55 degrees from H to. D ; and from the point n draw n E a parallel to E c, which shews the declination and sun's path as before. Thus though you have no scales or tables of the sun's de- clination at hand, yeti see it is possible to find the hour and VOL. vllt. Li
RkJQdWJsaXNoZXIy OTcyMjk=