rightly divided into 90 Degrees, and where∣in
also there is rightly to be described the Horary
Line according to the Scheme; together with the
Horary Points, also according to the Scheme.
[ 10]
2. To perfect this Sun-Dyal three things in
general are necessary; first, The description of
the Hours in the given Plain; Secondly, The [ 20]
contrivance of the Style, that is, as to the
Form and Altitude of it, and in what place it
ought to be fix'd; And, Thirdly, The Applica∣tion
and Disposition of the Dyal it self thus fi∣nish'd.
It is to be noted, first in general for the descri∣bing
of the Hours, that there are commonly pre∣suppos'd
two right Lines cutting each other
Cross-ways to right Angles, whereof the one is
the Meridian Line, or Line of the 12th Hour; [ 30]
the other is the Occult Line, which cuts the first
Cross-ways to right Angles: And this is also
vulgarly called the Line of Hours, because
therein are designed the Horary Points; but more
properly the Aequinoctial Line, because it repre∣sents
the Aequinoctial Circle, which is the prime
Rule of all Hours.
Note, Secondly, That all Hours (at least Astro∣nomical,
or Equal, are distinguished proportio∣nably
among themselves by an Interval of 15 [ 40]
Degrees orderly towards the Aequinoctial Circle;
because in the space of one of these Hours the
Sun runs 15 Meridians, which pass through so
many Degrees of the Aequator, whereupon an
Astronomical Hour is thus defin'd. An Hour
is the Space of Time, in which the Sun runs
through 15 Meridians, or in which 15 Degrees
of the Aequator ascend above the Horizon, as
hath been before observed.
Note, Thirdly, That there is need of a Plum-Line, [ 50]
or Perpendicular, for the right placing and
ordering of the Dyal, the better to examine whe∣ther
it be Parallel to the Horizon, or Perpendi∣cularly
Vertical, &c.