On That Difference of Various Places Which We Call the Difference of Longitude.

The number which they use as divisor (4800) is the numbel' of the yo}anasof the circumference of the earth, for the difference between the spheres of the meridians of the two places stands in the same relation to the whole circumference of the earth as the mean motion of the planet (sun) from one place to the other to its whole daily rotation round the earth.