CHA P. XXIX.

Of comparing the Times in one Place with those of another.

PROPOSITION 1.

Having the Hour in one given place, to find the Hour of another place given.

HE Place for which the Hour is given being brought to the Brafs Meridian, and the Index to 12, turn the Globe till the other Place come under the Brafs Meridian; and the Index will point to the Hour in the other Place.

PROPOSITION II.

Having the Hour in any place given, to show all the places on the Globe, in which 'tis then Mid-day or Mid-night, or any Hour you pleafe. The Problem fhould be propofed and folved of the Earth itself, it being a Property of the Earth, if we were to proceed fcientifically; and this we understand of many of the following Problems.

BRING the Place to the Meridian, and the Index to the Hour of the Place; then turn the Globe till the Index points to 12, and you fee under the upper Part of the Brafs Semicircle, all the Places where 'tis Mid-day, and in the lower Part

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where

SECT. VI. where 'tis Mid-night: and for any other Hour turn the Globe till the Index point to it, and you have the Places where 'tis fuch an Hour under the Brafs Meridian.

PROPOSITION III.

Having the Altitude of the Sun, the Day of the Year, and the Latitude of the place, to find the Hour for that Altitude.

ELEVATE the Pole for that Latitude, and find the Sun's Place in the Ecliptic, and bring it to the Meridian; then fixing the Quadrant of Altitude at the Zenith, and the Index at 12, move the Globe and the Quadrant till the Sun's Place come under the Degree of Altitude marked on the Quadrant; and the Index will point to the Hour.

PROPOSITION IV.

Having the Point the Sun is in at any Hour of a given Day, and the Latitude of the place, to find the Hour.

WORK as in the preceding Propofition, and bring the Quadrant to the Point, and the Sun's Place under the Quadrant, and the Index will fhow the Hour. What Point the Sun is in, is known by the Mariner's Compass.

PROPOSITION V.

To know by the Globe, (when the Sun fhines) the Hour in a place whofe Latitude is given.

ELEVATE the Globe for the Latitude, and make it's Axis point to the North; then fix a Needle perpendicular in the Sun's Place under the Meridian,

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Meridian, the Hand being at 12; turn the Globe till the Needle be under the Sun, and makes no Shadow on the Globe; and the Index will show the Hour.

PROPOSITION VI.

Having the Hour, as we reckon it, to know the Hour from Sun-rifing, i. e. the Babylonifh Hour, or the Hour at Norimberg.

THE Babylonians of old, and the People of Norimberg now, count twenty four Hours, from Sun-rifing to Sun-rifing the next Day. Elevate the Pole for the Latitude, and bring the Sun's Place to the Meridian, and the Index to 12; turn the Globe till the Index point to the Hour given, then the Globe being fixed, bring the Index back to it, then turn it from Weft to Eaft till it come to the Horizon, and count the Hours from it to the Index Eaftward; aud thefe are the Hours fought.

PROPOSITION VII.

Again, having the Babylonish Hour, to find the Hour by our Reckoning, i, e. from twelve at Day, or Night.

ELEVATE the Pole for the Latitude, and bring the Sun's Place to the Horizon on the Eaft, and the Index to it, and turn the Globe till the Index points to the Hour from Sun-rifing; then bring the Index back to 12, and turn the Globe till you bring the Sun's Place under the Meridian, and you'll fee how many Hours 'tis past 12 or before 12, by your reckoning.

PROPOSITION VIII.

Having the Hour, as we reckon it, to find bow many Hours are past fince the Sun fet last; that is, the Italian Hour.

THEY now in many places of Italy, as of old in Greece, begin their Day at Sun-fet; which lafts till the next Sun-fetting,

TO find their Hour; elevate the Globe for the Latitude, and bring the Sun's Place to the Meridian, and the Index to 12; turn the Globe till it point to the Hour given, then bring the Hand to 12, and turn the Globe to the Eaft till the Sun's Place come to the Horizon, and count the Hours from 12 to the Index.

PROPOSITION IX.

Having the Italian Hour from Sun-fetting, to find the Hour, as we reckon it, from Mid-day or Midnight.

ELEVATE the Globe for the Latitude, and bring the Sun's Place to the Meridian, and the Index to 12; turn the Globe Weftward till the Index point to the Hour given, then the Globe being fixed, bring back the Index to 12, then turn the Globe till the Sun's Place come under the Meridian, and count the Hours from 12 to the Index Eastward; and you have the Hours from Midday or Night, according to our reckoning,

PROPOSITION X.

Having the Hour, as we reckon it, in a given Day, ta find the Jewish Hour, as they and others reckoned. IT

IT appears from the Difcourfe of Christ, about the hiring of Labourers to the Vineyard, that the Jews, and other Nations before Aftronomy was cultivated, divided the Day, from Sun-rifing to Sun-fetting, into twelve Hours, and the Night into as many, which are called Planetary Hours for another Reafon; but they are rather to be called unequal Hours: for feeing neither Days nor Nights are equal, but increase the one half of the Year, and decrease the other, except under the Equator; the Hours must be fometimes longer, and fometimes shorter; tho' near the Equator there is no great Alteration, as we fhewed Chap. xxv. and therefore they that are far from the Equator, as the Europeans, never ufed that Way, but only they in the Torrid Zone, or not far from it.

THE Problem then may be propofed more clearly thus: Having the equal Hour in any Day, to find the unequal Hour, which is the twelfth part of the Time the Sun is above the Horizon; but the equal Hour is the twenty fourth part of the Time the Sun takes in going from the Meridian till it returns to it; which is the Aftronomical Day.

TO folve the Problem: Elevate the Globe for the Latitude, bring the Sun's Place to the East Horizon, and the Index to 12, and turn the Globe 'till the Sun's Place come to the Weft: Thus you find the Length of that Day. Then find the Hour from Sun-rifing or Sun-fetting, if the Hour given be after Sun-fetting, by Prop. vi. and viii. and fay, as the Length of the Day (or Night) in Hours is to twelve Hours; fo are the Hours from Eaft (or Weft) to the Jewish Hour.