Page:Cyclopaedia, Chambers - Volume 1.djvu/912

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Weft, till the Index point at the given Hour: Thus again will the Place requir d be found under the Point of the Me- ridian before noted.—

If at the fame time, you note all the Places which are under the fame Half of the Meridian with the Place found; you will have all the Places to which the Sun is then in the Meridian : And the oppofite Half of the Meridian will fhew all the Places, in which it is then Midnight.

V. A Place being given in the torrid, Zone, to find the two Days in the Tear wherein the Sun is vertical to the fame.

i° Bring the given Place to the Meridian ; and note the Degree of the Meridian correfponding thereto. z° Turn the Globe about, and note the two Points of the Ecliptic paffing thro' that Degree. ?° Find what Days the Sun is in thofe Points of the Ecliptic: For on thofe Days he is ver- tical to the given Place.

VI. To find thofe Places in the Torrid Zone to which the Sun is Vertical on agive?z Day.—

Bring the Sun's Place in the Ecliptic to the Meridian : Then turning the Globe round, note all the Places which pafs thro' that Point of the Meridian. Thofe are the Places re- quired.

After the fame manner are found what People are AfoiU for any given Day. See Ascii.

VII. A Place being given in the Frigid Zone, to find on what Days of the Tear the Sun does not rife 5 and on what T)ays he does not fet to the fame.

i° Count as many Degrees in the Meridian from the M- quator towards the Pole, as Is the Diftance of the given Place from the Pole. 1* Turning the Globe round, note all the Points of the Ecliptic pafftng thro' each Point noted in the Ecliptic : By this means you will have the Arches which the Sun defcribes while he neither rifes, nor fets ; and the Points themfelves give the Places of the Sun, when he neither rifes nor fets, at the Beginning and Ending. 3 Find what Days of the Year the Sun is in thofe Places: Thefe are the Anfwer to the Queftion.

VIII. To find the Latitude of the Places wherein any given Day is of any given Length*

i° Bring the Sun's Place for the given Day to the Ecliptic, and fet the Index to the Hour of twelve. z° Turn the Globe, till the Index point at the Hour of rifing or fetting. 4 Raife and deprefs the Pole till the Sun's Place appear in the Eaftcrn or Wetiem Side of the Horizon. Then will the Pole be duly elevated, and confequently the Latitude given.

IX. To find the Latitude of thofe Places in the Frigid Zone, where the Sun docs not fet for a given Number of Days.

i° Count fo many Degrees from the next Tropic, towards the Equinoclial Point, as there are Units in half the Number of the given Days ; by reafon, the Sun in his proper Motion, ooes nearly a Degree every Day. 2 Bring the Point of the Ecliptic, thus found, to the Meridian: Its Diftance from the Pole will be equal to the Elevation of the Pole, or Lati- tude of the Places requir'd.

X. Any Hour of the Day, or Night being given, to fhew all thofe Places to which the Sun rifes, and fets ; where it is Noon, or Midnight ; and where Day, or Night.

i° Find what Place the Sun is at that time vertical to, as already taught. 2^ Let this Place be brought to the Ze- nith of the wooden Horizon, i. e. elevate the Pole as the Latitude of that Place requires. Then, will the Places on the Eaftern Side of the Horizon, be thofe the Sun is fetting to ; and on the Weftcrn Side, thofe he rifes to : Thofe un- der the upper Semicircle of the Meridian, have it Noon 5 and thofe under the lower, Midnight. Laftly, to thofe in the upper Hemifphere it is Day; and to thofe in the lower, Night.—

Hence, as, in the Middle of an Eclipfe, the Moon is in the Degree of the Ecliptic oppofite to the Sun's Place ; by the prefent Problem it may be fliewn what Places of the Barm then fee the Middle of the Eclipfe; and what, the Beginning, or Ending.—

XL To find what Places of the Earth a Planet, e. gr.

the Moon, is vertical to, any day of the Tear.

i° Mark the Planet's Place on the Globe, ss above taught. »° Eilng this Place to the Meridian ; and note the Degree

over it. $° Turn the Globe round; the Places which pafs under the Point, are thofe required. — •

XII. The Declination of a Star, or any other Phsno- menon given ; to find what Parts of the Earth the fame is vertical to.

Count as many Degrees in the Meridian, from the JEqua- tor towards one Pole, as are equal to the given Declina- tion ; viz. towards the North, it the Declination be North- ward; and towards the South, if the Declination be South. Then, turning it round, the Places that pafs thro' the Ex- tremity of this Arch in the Meridian, are the Places re- quired. — ■

XI II. To determine the Place of the Earth where any Star, or other Celeftial Phenomenon will be Vertical at a given Hour.

i° Elevate the Pole according to the Latitude of the Place, from whofe Noon or Midnight the Hours are num- ber 'd. 2 Bring the Sun's Place tor that Day to the Meri- dian, and fet the Index to Twelve a-Clock. 5 Determine the Place of the Star on the Surface of the Globe, and bring it to the Meridian: The Index will /hew the Difference of* Time between the Appulfe of the Sun and Star to the Me- ridian of the Place: Note the Point of the Meridian over the Place of the Star. 4. Find in what Piaces of the Earth it is then Noon, and fet the Index to Twelve a-Clock. 5 U. Turn the Globe towards the Weft, till the Index have pafs'd over the Interval of Time between the Culmination of the Sun and Star. Then, under the Point of the Meridian be- fore obferved, will the Place required be found.

And hence may be found what Place a Star, or other Phenomenon rifes or fets to at any given time.—

XIV. To place the Globe in fuch manner, trader any given Latitude, as that the Sun fihall illumine all thofe Regions, which he atlually illumines on Earth.

j° Rectify the Globe, i. e. Elevate the Pole according to the Latitude of the Place: Bring the Place to the Meri- dian ; and fet the Globe North, and South by the Compafs : Thus, ih&Globe having the fame Situation to the Sun, as the Earth has ; that Part thereof will be illumined, which. is illumined on Earth.

Hence, the Globe being fituate in the fame manner, when the Moon mines, it will inew what Parts are then illumined by the Moon.

And, in the fame manner, may we find where the Sun and Moon rife and fet at any given Time.

XV. To find the Difiance of t-mPlaces on the Globe..

Take the given Places in the Compafles ; and apply them to the Equator. The Degrees they there fubtend, being redue'd into Miles, Leagues, or the like, give the Diftances required. See Degp.ee, Mile.^c.

The fame may be done, and more commodioufly, by laying the graduated Edge of the Quadrant of Altitude over the two Places; and noting the Degrees intercepted. — ■

GLOBULAR Chart, a Reprefentation of the Surface, or fome Part of the Surface, of the Terraqueous Globe, upon a Plane ; wherein the Parallels of Latitude are Circles nearly Concentric ; the Meridian's, Curves bending towards the Poles; and the Rhumb-lines alio Curves. See Chart, and Projection.

The Merits of this Chart confift in this, that theDiftancea between Places upon the fame Rhumb, are all meafur'd by the fame Scale of equal Parts, and the Diftances of any two Places in the Arch of a great Circle, is nearly reprefented in this Chart by a Straight Line. — Hence, Land Maps made according to this Projection, would indifputably have great Advantages above thofe made any other way. See Map.

But for Sea Charts, and the Ufes of Navigation, 'tis yet controverted, whether the Globular Chart be preferable to Mercator's, where the Meridians, Parallels, and particularly the Rhumb-lines, are all ftraight Lines; inafmuch as ftraight Lines are found more eafy to draw, and manage than Curves, efpecially fuch as the Rhumb-lines on the Globular Chart are. See Mercator, Rhumb, &c.

This Projection is not new, tho' not much taken notice of till of late. It is mention 'd by Ptolemy, in his Geography 5 as alfo by Slundevil in his Exercifes.

Globular Sailing ; fee Great Circle Sailing.

GLOBULE, Globulus, a little Globe; call'd alfo a Spherule. See Globe.

Thus the Cruor, or red Particles of the Blood are call'd Globules of the Blood, on account of their Rednefs, and Smalnefs. See Cruor.

The Microfcope difcovers the Blood to confift of red, globular Particles, fwimming in a limpid, tranfparent Water,

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