The quantities opposite the different numbers of hours, minutes, and seconds, are to be subtracted to obtain the equivalent interval of mean solar time for any period.

The quantities opposite the different numbers of hours, minutes, and seconds, are to be added to obtain the equivalent interval of sidereal time for any period.- Vide Table of Equivalents, page 489 of the "Nautical Almanac." This table, and the preceding are calculated, from the ratio of a sidereal to a mean solar day-twentyfour hours of mean time being equivalent to 24.. 3.. 56.5554 sidereal time.

TABLE III.'

FOR CONVERTING SPACE INTO TIME, and VICE VERSA.

Young's Refractions have been selected from among those by different eminent

Astronomers, given in Dr. Pearson's Tables.

BB