a Pofition of the Globe as is proper to the City in which I live, viz. Chichester, whofe Latitude is 50° 56', by Obfervation; and the Time or Seafon of the Year in which I write this, viz. May the 30th.

A Figure of the Globe (or more properly the Sphere) as rectified to this Place, and representing the Pofition of the Heavens (with regard to us) this Morning, is here below fubjoin'd.

The Oblique Pofition of the Globe in this Figure occafions feveral Triangles, both Right and Obliqueangled, to be made on its Superficies; amongst others I fhall make choice of the Right-angled Triangle

POS

POS to ferve my Purpose here: This Triangle is thus made and conftituted.

1. The Side or Leg PO, is part of the great Brafs Meridian, and equal to the Latitude, viz. 50% 561.

2. The Side OS is an Arch or Part of the Hori zon, equal to the Sun's Amplitude from the North at Rifing or Setting, and is 519 48.

3. The Side or Hypothenule PS is the Arch of another Meridian, fuppofe the Equinoctial Colure, and it is equal to the Sun's Distance from the Pole or Complement of its Declination, viz. 66° 57'.

4. The Angle OPS is the Hour from Midnight, and is meafured on the Equinoctial, between the Brafs Meridian and Equinoctial Colure; and will be found to be 57° 22, or 3 Hours 49+ Minutes.

5. The Angle PSO is the Angle of the Sun's Pofition at the given Time, whofe Measure is the Arch of a great Circle comprehended between the Horizon and Equinoctial Colure at the Distance of 90°; and will be found to be 579 32

VI. The Angle POS is the Right-angle contained between the Horizon and Meridian, whofe Measure is the Quadrant of Altitude fixed in the Zenith, and laid to the Eaft or Weft Points of the Horizon.

Having thus defigned the Parts, and Quantity of each Part of the Triangle, we will now proceed to the Solution of the fix Cafes of a Right-angled Spherical Triangle by the Globe; as followeth.

Cafe i.

Given {

The Hipothenuse

PS = 66 57

and the Oblique-angle at P = 57 22

Requi

Required

{

The Sun's Amplitude S O.;
The Latitude of the Place PO;
The Angle of the Pofition P SO.

In order to folve this Cafe, numerate 57° 22′ on the Equinoctial from Y, and bring that Point to the Brafs Meridian; and there keep the Globe faft in the Meridian; then elevate or deprefs the Globe in the Horizon, 'till 66° 57' (before marked) on the Colure does juft touch the Edge of the Horizon; then will the Brafs Meridian reft in the Horizon at 50° 56' PO the Latitude of the Place; and the Arch of the Horizon OS, intercepted between the Meridian and the Colure, will be feen to be 51° 48' Amplitude. The Angle PSO alfo measured by the Quadrant of Altitude, or with the Compaffes, will be found 57° 32'.

=

the

The Angle of Pofition P SO;

To frame the Triangle, and folve this Cafe, elevate or deprefs the Globe, 'till 662 57' on the Colure, touches 51° 48′ in the Horizon, reckoned from the North Point; then fhall the Horizon interfect the Brafs Meridian in 50° 56' PO. And the Degrees intercepted, between the Brass Meridian and Equinoctial Colure on the Equinoctial, give the Quantity of the Angle SPO 57° 22'. The Angle PS O being measured, will be found 578 32'.

Note,

Note, If the other Leg PO had been given instead of SO, you needed only to have rectified the Globe to the Latitude, and turned it about till 66° 57' of the Colure had touched the Horizon; for then would the Triangle have been conftituted, as before; and its Parts in like manner been found.

Firft rectify the Globe to the given Latitude 509. 56', and turn the Globe about, 'till 57° 22' be intercepted on the Equinoctial between the Brafs Meridian and the Equinoctial Colure; then fhall the Hypothenufe PS, measured on the Brafs Meridian, be found to be 66° 57', for the Complement of the Sun's Declination; the Leg or Arch of the Horizon O S will appear to be 519 48', for the Amplitude; and the Angle PSO when measured, will be found 57° 32'.

Let the Equinoctial Colure and Brafs Meridian make an Angle of 57° 221, and having there fixed the Globe, elevate or deprefs it, 'till the faid Colure interfects the Horizon in 51° 48'; then fhall the CoDeclination PS, measured on the Meridian, be found 66° 57'; the Latitude PO will be feen to be 50° 56′, on the graduated Meridian, and the Angle PSO 57° 32′ as before.

Rectify the Globe to the given Latitude, and turn it round 'till the Equinoctial Colure touch the Point of 51° 48' on the Horizon; this being done, you will find the Co-Declination PS = 66° 57′; the Hour from Midnight S PO = 57° 22' ; and the Angle of Pofition PSO 57° 32', when meafured, as before directed.