Celestial and T’errejlrial Globes . 331

the length of the day at London, or else-where, when the sun is in the first pointof Cancer, or any other parallel of his de-clination, viz.

354. Subtract the fun’s ascensional dis-serence in time from six in the morning,the residue is the time of his rising; add itto six in the evening, and it gives the timeof his setting ; then doubling the first youobtain the length of the night, and thedouble of the last will be the length of theday. And after this manner all these par-ticulars may be found to every intermediatepoint of the ecliptic in all latitudes.

As the rising and setting of some of theprincipal fixed stars are mentioned by ancientwriters, as criteria, by which to judge ofthe commencement of seasons, and the be-ginning of times set apart for religion, hus-bandry, politicks, &c. we have judged itnecessary to add the following problems, asa farther elucidation of the two former, art.302 and 303.

PROBLEM