ECLIPTIC. See Encycl. both under ECLIPTIC and in ASTRONOMY-Index. It was observed in ASTRONOMY, Encycl. n. 407, that the obliquity of the ecliptic has been found gradually to decrease. This was observed, among others, by La Lande, who, in the third edition of his astronomy, reckoned the secular di-
mination of this obliquity at 50 seconds. From a new examination, however, of ancient observations, he has since found reason to estimate it at only 36 seconds; but whether this be perfectly accurate, is very doubtful. The mean obliquity was determined for the 1st of January 1793, with circular instruments, by Mechain at Barcelona, and Piazzi at Palermo, to be . Yet the observation of the summer solstice of 1796, by Mechain and Le Franc, gave 11 seconds more: which was justly considered as a perplexing circumstance. But, as one of the ablest of our literary journalists observes, might not this difference arise from the uncertainty of our tables of refraction, as affected by the hygroscopic variations of the atmosphere?