Cekjlial and Herrejlrial Globes. 213

The knowledge of that particular pointon the terrestrial equator, where its inteivsection with the celestial ecliptic happensto fall at the time of a vernal equinox,points out that place upon the earth to whichthe fun is vertical at that time; and fromthe knowledge of this we obtain the time of:its passage over any meridian upon the globe,for every day of the year.

The conformity of the degrees of rightascension, with those of terrestrial longitude,happens but upon one moment of the 24hours, in a natural day; when the first pointof Aries is on the meridian of London,the first degree of right ascension is on thismeridian also ; and the signal to confirmthis is, when a star of the second magnitudemarked y near the extremity of the wingof Pegasus, is upon the meridian; at thatinstant, the equinoctial colure will be uponthe meridian also; for this colure passesthrough the first point of Aries and thatstar.

This is the moment, in which each ofthe 360 degrees of right ascension in the ce-lestial sphere, is perpendicular to every likedegree of terrestrial longitude; at whichP 3 ' time