Page:Cyclopaedia, Chambers - Volume 1.djvu/911

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eafily note the fame, there. 4" After the fame manner may you proceed from this to the neighbouring Conftellations ; till you have learnt them all. See Star.

If the Planets be reprefented on the Glebe, after the man- ner above defcribed, by comparing them with the neigh- bouring Stars, you will likewife know the 'Planets. See Planet.

VIII. To find the Sun's oblique Afcenfion, his Eaftern Amplitude, and Azimuth, with the time of Rifing.—

l° Rectify the Globe for the Hour of XII ; and bring the Sun's Place to the Eaftern Side of the Horizon : Then, the Number of Degrees intercepted between that Degree of the ./Equator now come to the Horizon, and the Beginning of Aries, is the Sun's Oblique Afcenjion. 1 9 The Degrees on the Horizon intercepted between the Eatt Point thereof, and the Point wherein the Sun is, is the Ortive, or rising Am- plitude. 3 The Hour pointed toby the Index, is the Time of the Sun's Rifing. 4 Turning the Globe, till the Index points to the prefent Hour ; lay the Quadrant to the Sun's Place ; the Degree cut by the Quadrant, in the Horizon, is the Sun's Azimuth. See Azimuth, Oblique, gfc.

IX. To find the Sun's Oblique Defcenfion, Weftern Am- plitude, and Azimuth, -with the Time of Setting.

The Solution of this Problem is the fame as that of the former ; excepting that the Sun's Place mutt be here brought to the Weftern Side of the Horizon ; as, in the former, it was to the Eaftern. See Descension.

X. To find the Length of Day and Night.

i° Find the Time of the Sun's rifing ; which being num- ber'd from Midnight, the Double thereof gives the Length of the Night. 2 Subflract the Length of the Night from the whole Day, or 24 Hours ; the Remainder is the Length of the Day. See Day, and Night.

XI. To find the Rifing, Setting, and Culminating of a Star, its Continuance above the Horizon, for any Place '. and Day ; together ivith its oblique Afienfion, and De- fcenfion ; and its Eaflern and Weftern Amplitude and Azimuth.


 * .i° Adjuft the Globe to the State of the Heavens, at 12

a-G. lock, that Day. z° Bring the Star to the Eaftern Side of rl ie Horizon : Thus will its Eaflern Amplitude, and Azi- muth ', and the Time of rifing be found • as already taught of tlv.e Sun. 3 Bring the fame Star to the Weftern Side of the Horizon : Thus will the Weftern Amplitude and Azi- ynuth, and the Time of fetting be found. 4 The Time of Rifi-ng fubtracted from that of Setting, leaves the Conti- nuance of the Star above the Horizon. — 5 This Continuance above the Horizon lubtracted from 24 Hours, leaves the Timie of its Continuance below the Horizon. 6" Laftly, the H' cur t° which the Index points, when the Star is brought to the Meridian; gives the Time of Culmination. See Rising^ Setting, Culminating, &c.

XII. To find the Altitude of the Sun, or a Star, for any give •» Hour of the Day or Night.

t" Adj uft the Globe to the Pofition of the Heavens ; and turn it till the Index point at the given Hour. 1" Fix on the Quadravnt of Altitude, at 90 Degrees from the Horizon^ and brine i t to the Sun's or Star's Place. The Degrees of the Quadra. nt intercepted between the Horizon, and the Sun or Star is the- Altitude required. See Altitude.

X3II. The .Altitude of the Sun by Day, or of a Star by Jfigbt being given, to find the Time of that Day, or Night.

1° Rectify the Globe as in the preceeding Problem. 2° Turn the Globe, and Quadrant till fuch Time as the Star, or Degree of the Ecliptic the Sun is in ; cut the Quadrant in the given Degree of Altitude; then does the Index point at the Hour fought. See Time, Hour, Sec.

XIV. The Azimuth of the Sun, or a Star, given ; to find the Time of Day, or Night.

Rectify the Globe ; and bring the Quadrant to the given Azimuth in the Horizon : Turn the Globe, till the Star come to the fame : Then will the Index ftiew the Time.

XV. To find the Interval of Time between the Rifings of two Stars ; or their Culminations.

i° Raife the Pole of the Globe fo many Degrees above -.the Horizon, as is the Elevation of the Pole of the Place;

2 Bring the firft Star to the Horizon ; and obfervc thd Time the Index points to. 3° The fame do by the other Star. Then fubtracting the former Time from the latter; the Remainder is the Interval between the Rifings.

After the like manner is the Interval between two Culmi- nations found; by bringing both Stars to the Meridian.

XVI. To find the 'Beginning and Ending of the Crepuf- culum, or Twi-light.

i° Reflify the Globe ; and fet the Index to the XII th Hour; the Sun's Place being in the Meridian. -2° Take' the Sun's Place, and turn the Globe Weft ward, as alfo the Quadrant of Altitude, till the Point oppofite to the Sun's Place cut the Quadrant of Altitude in the i8 ,h Degree above the Horizon. The Index will Ihew the Time when the Twi- light commences in the Morning. 3" Taking the Point op- pofite to the Sun ; bring ir to the Eaftern Hemifphere, and turn it, till it meet with the Quadrant of Altitude in the I8" 1 Degree: Then will the Index fhew the Time when Twi-light ends. See Crepusculum. ■ f

Terrcftrial Globe, is an artificial Sphere, on whofe Sur- face are delineated the principal Places of the Earth, in their proper Situations, Distance's, cf?c. together with the Cir- cles imagin'd on the Surface of the terrettrial Sphere. See Earth.

TheUfe of the. Terrcftrial Globe, is to exhibit the fe- veral Affections, and Pha;nomena of the different Places of the Earth, depending on Magnitude, l3c. in an eafy, ob- vious manner, without the Trouble of Trigonometrical Cal- culation. See Geography.

To conftruB a Terrcftrial Globe.

The Conftruflion of a Terreftrial Globe, whether of Me- tal, or Plaifter, Paper, gfc is the fame as that of a Cele- ftial. The fame Circles are delineated on both : And as for the Places, viz. Cities, Towns, f$c. they are laid down from the Longitudes, and Latitudes given ; as the Stars are from their right Afcenfions and Declinations.

Hence, all Problems depending on the Circles, may be equally wrought on either Globe ; as the Afcenfions, Def- cenfions, Amplitudes, Azimuths, Rifings, Settings, Alti- tudes, ($c. of the Sun ; the Lengths of Day and Night ; Hours of the Day and Night ; Crcpufcula, Z3c.

We fhall here, therefore, only give what is peculiar to the Terreftrial Globe.

Ufe of the Terreftrial Globe.

Problem. I. To find the Longitude and Latitude of any Place delineated on the Globe.

Bring the Place to the graduated Side of the Brafs Meri- dian : The Degree of the Meridian it cuts, is the Latitude required ; and the Degree of the JEquator at the fame time under the Meridian, is the Longitude required.

II. The Longitude and Latitude given, to find theTlace on the Globe.

Seek, in the JLquator, the given Degree of Longitude/ and bring it to the Meridian : Then count from the Equa- tor on the Meridian the Degree of Latitude given towards this or that Pole, as the Latitude is either North, or South. The Point under this is the Place requir'd.

III. To find the Antoeci, 'Periotci, and Antipodes of any Place.

i° The given Place being brought to the Meridian ; count as many Degrees on the Meridian from the Equator towards the other Pole. The Point thus arrived at,' is the Place of the Antoeci. See Antoeci. 2° Note the Degrees of the Meridian over the given Place and its Antoeci ; and turn the Globe till the oppofite Degree of the Equator, come under the Meridian ; or, which amounts to the lame, till the In- dex, which before flood at XII, com e to theother XII: Then will the Place correfponding to the former Degree, be the Pcriceci ; and the latter, that of Antipodes. See Pe- rio;ci, and Antipodes.

IV. To find what (Place of the Earth the Sun is Verti- cal to at any Time affigned.

1" Bring the Sun's Place found in the Ecliptic to the Me- ridian ; and the Index to the Hour of XII ! Noting what Point of the Meridian correfponds thereto. 2° It the given Hour be before Noon ; fubtraft it from twelve Hours ; and turn the Globe towards the Weft, till the Index point at the Hours remaining. Thus will the Place requir d be under the Point of the Meridian before "oted. 2 It the Hour be Afternoon, turn the Globe in the fame manner toward^the