ECL 



ECO 



that the earth appears to describe, to an 

 eye placed in the sun. 



By a long series of observations, the 

 shepherds of Asia were able to mark out 

 the sun's path in the heavens ; he being 

 always in the opposite point 4o that 

 which comes to the meridian at midnight, 

 with equal, but opposite, declination. 

 Thus they could tell the stars among 

 which the sun then was, although they 

 could not see them. They discovered 

 that this path was a great circle of the 

 heavens, afterwards called the ecliptic, 

 which cuts the equator in two opposite 

 points, dividing it, and being divided by 

 it into two equal parts. They farther ob- 

 served, that when the sun was in either 

 of these points of intersection, his circle 

 of diurnal revolution coincided with the 

 equator, and therefore the days and 

 nights were equal. Hence the equator 

 came to be called the equinoctial line, 

 and the points in which it cuts the eclip- 

 tic were called the equinoctial points, 

 and the sun was then said to be in the 

 equinoxes. One of these was called the 

 vernal, and the other the autumnal equi- 

 nox. See EQUINOXES. 



ECLIPTIC, obliquity of, is the angle 

 which its plane makes with that of the 

 equinoctial. The inclination of the e- 

 quator to the ecliptic is measured by the 

 arch of a great circle intercepted between 

 their poles, which was taken with very 

 great accuracy by Dr. Maskelyne, in the 

 year 1769, and found to be 23 28' 10", 

 or 23 46944. It was formerly found by 

 Dr. Bradley to be 23 28' 30", who sup- 

 posed that there was a gradual approach 

 nf the ecliptic to the equinoctial, at the 

 rate of 1' in 100 years. The mean obli- 

 quity of the ecliptic is augmented by 9", 

 when the moon's ascending node is in 

 the vernal equinox. It is, on the contra- 

 ry, diminished 9'', when the node is in 

 the autumnal equinox, and it is equal to 

 the mean, when the node is in the co- 

 lure of the solstices. This change of 

 the inclination of the earth's axis to 

 the plane of the ecliptic was called 

 the nutation of the axis by Sir Isaac New- 

 ton. 



Dr. Bradley discovered a general and 

 periodical motion in all the stars, which 

 alter a little their relative situations. To 

 form an idea of this motion, let us sup- 

 pose that each star describes annually a 

 small circumference parallel to the eclip- 

 tic, whose centre is the mean position of 

 the star, and whose diameter, as seen 

 from the earth, subtends an angle of 

 about 40" ; and that it was in that circum- 

 YOL. IV. 



ference as the sun in its orbit, but so that 

 the sun always precedes it by 90. This 

 circumference, projected upon the sur- 

 face of the celestial sphere, appears un- 

 der the form of an ellipse, more or less 

 flattened, according to the height of the 

 star above the equator, the smaller axis 

 of the ellipse being to the greater axis 

 as the sine of that height to the radius. 

 These periodical movements of the 

 stars have received the name of aber- 

 rations of the fixed stars. See ABER- 

 RATION. 



ECLIPTIC, in geography, a great circle 

 on the terrestial globe, not only an- 

 swering to, but falling within the plane 

 of the celestial ecliptic. See GLOBES, 

 use of. 



ECLOGUE, in poetry, a kind of pasto- 

 ral composition, or a small elegant poem, 

 in a natural simple style. 



The eclogue, in its primary intention, 

 is the same thing with the idyllium, but 

 custom has made some difference be- 

 tween them, and appropriated the name 

 of eclogue to pieces wherein shepherds 

 are introduced, and idyllium to those 

 written like eclogues, but without any 

 shepherds inthenr. T.he eclogue then is 

 properly an image of pastoral life, upon 

 which account the matter is low, and its 

 genius humble. Its business is to de- 

 scribe the loves, sports, piques, jealou- 

 sies, intrigues, and other adventures of 

 shepherds ; so that its character must be 

 simple, the wit easy, and the expression 

 familiar. Then the true character of the 

 eclogue is simplicity and modesty; its, 

 figures are neat, the passions tender, the 

 motions easy, and though sometimes it 

 may have little transports and despairs, 

 yet it never rises so high as to be fierce 

 or violent. Its narrations are short, de- 

 scriptions little, the thoughts ingenious, 

 the manners innocent, the language 

 pure, the verse flowing, the expressions 

 plain, and all the discourse natural. 



ECONOMY, political. Political econo- 

 my is the science which treats of the 

 wealth of nations. Its object is to ascer- 

 tain, in the first place, wherein wealth 

 consists, and then to explain the causes 

 of its production, and the principles on 

 which it is distributed through the differ- 

 ent orders of society. It likewise endea- 

 vours to point out the tendency, which 

 any political regulations may have'to fa- 

 vour or to injure the productions or most 

 advantageous distribution of wealth. Such 

 is its peculiar object, and consequently, 

 though writers on political economy may 

 frequently treat on the more important 



P P 



