Page:Philosophical Transactions - Volume 004.djvu/51



Here take notice, that the Sun or the Earth passetb the 12. Signes, or makes an entire revolution in the Ecliptick in 365 days, 5 hours, 49 min, or there about, and that those days, reckon'd from noon to noon, are of different lengths; as is known to all, that are vers'd in Astronomy. Now between the longest and the shortest of those days, a day may be taken of such a length, as 365 such days, 5. hours &c. (the same numbers as before) make up, or are equall to than revolution: And this is call'd the Equal or Mean day, according to which the Watches are to be set; and therefore the Hour or Minute shew'd by the Watches, though they be perfectly Iust and equal, must needs differ almost continually from those that are shew'd by the Sun, or are reckon'd according to its Motion. But this Difference is regular, and is otherwise call'd the Æquation, and here you have a Table, that shows it. Rh