CHAP. I.
The several Sorts of SVN-DYALS.
DYALS are either moveable, being such that may be carryed about them, as the Cylinder and certain little Boxes, whose [ 10] Needle (like Indexes) are touch'd with the Load-Stone; or Immoveable, that is, fixt to some certain place. They are also Regular, or Irregular; Regu∣lar are those that are described in a Plain, dispo∣sed towards some one determined principal part of the World; For Example, direct East, or direct West. The Irregular are those which do not di∣rectly point to those principal parts of the World, but rather decline from them.
1. Of those Regular, the first is the Horizon∣tal; [ 20] the second, the Vertical Southward; the the third, the Vertical Northwards; the fourth, the Meridian East; the fifth, the Meridian West; the sixth, the Aequinoctial above; the seventh, the Aequi∣noctial below; the eighth, the Polar above; and the ninth, the Polar beneath.
The Horizontal is that which is Aequidistant towards the Horizon.
The Vertical is that which is perpendicularly erected above the Horizon, and tends directly [ 30] towards the Vertical Point, and it is Parallel to the Primary Vertical Circle, and this is double, viz. North Vertical, as looking towards the other which is South Vertical.
The two Meridians, viz. the Eastern and West∣ern, each of them have their several ways which are Aequidistant from the Meridian Circle.
The two Aequinoctials are those which each of them their several ways are Aequidistant from the Aequator, the one above, the other beneath [ 40] the Horizon.
The two Polars are those which each of them their several ways, the one above, the other beneath, are Parallel to the Axis of the World.
The Irregular are either Declinant, or Inclinant.
The Declinant is that which is Aequidistant from any Vertical Circle, and it is therefore also not amiss called Vertical; but it declines from the Primary Vertical which is proporly so called, and it is of two sorts; for there is one which de∣clines from the South, either to the East, or West; and another that declines from the North, either to the East, or West.
The Inclinant is that which falls off from the Vertical Point, and Inclines towards the Horizon, as being not Aequidistant from it.
In respect of the Hours, Dyals are divided in Astronomical, Italick, Babilonick, Antient, or Ju∣daick.
The Astronomical declares equal Hours from Noon to Midnight, and from Midnight to Noon again; and it is principally in use all over Eu∣rope.
The Italick reckons equal Hours from West to West, so as that of the 24 Hours, that is said to be the first Hour which is the Hour of the Suns setting, and this would be called by us the 6th, 7th, or 8th Evening Hour, whereas on the con∣trary the Babilonick reckons equal Hours from Sun-rising to Sun-rising.
The Ancient, or Babilonick reckons unequal Hours, as Chronology shews more at large. I shall therefore treat only of Astronomical Dyals, because the knowledge of them leads to all the rest.