TER

709

TER

ave

m'.e

and

(•cl-

ay-

and

ily.

her

at

iber

to

ilh,

*ins

hit-

u li-the>ins

the

fid,

>1126

pe-

low

us;

hat

est-

by

this

;es,

:of

ted

'ey

. hents,si-lic-on,ra-ids,indiofnd-ag-thein-liebleSeeareersdomdortheble

ted

ate

her

anJ

ass

ilia

ior,

est

or

>’S,

ind

of

pa>

Demona, 10 miles S. E. of Palermo. Lon. 13. 44. E. Lat.38. 5. N.

Termini, or Termolt, a town of Naples, in the province ofCapitanata, and 70 miles N. E. of Naples. Lon. 15. 20. E.Lat. 41. 59. N.

TERMINUS, in Pagan worship, an ancient deity among theRomans, who presided over the stones or land marks called ter-mini, which were held so sacred, that it was accounted sacrilegeto move them.

TERNAI, the name given by Perouse to a very fine bay whichhe discovered on the coast of Tartary, in Lat. 45° 13' N. and inLon. 135° 9' E. of Paris .

TERNATE, the most northerly of the Molucca or CloveIslands in the East-Indies. It abounds in cocoa-nuts, bananas,citrons, oranges, almonds, and other fruits proper to the torridzone; but cloves are the most valuable produce. It is a mountain-ous country, in the possession of the Dutch, and its woods furnishabundance of game. Malava is the capital. Lon. 129. 0. E.Lat. 1.0. N.

TERNEUSE, astrong town and fort of Flanders , 12 miles S. E.of Flushing, 25 N. W. of Antwerp , and 5 from Axel. Lon. 3. 45.E. Lat. 51. 20. N.

TERN I, an ancient town of Italy , in the Papal territories, andin the duchv of Spolelto. The cathedral is a magnificent structure.Lon. 12. 40. E. Lat. 42. 34. N.

TERN OVA, a town of European Turkey in Bulgaria , 95miles N. E. of Sophia, and 200 N. W. of Constantinople . Lat.43. 0. N. Lon. 23. 35. E.

TERNSTROMIA, in botany, a genus of plants belonging tothe class polyandria, and order inonogynia. Calyx five-parted ;corolla one-petaled, wheel-shaped, with the border bell-shaped,five or six-parted ; anthers thick at the tip ; berry juiceless, two-celled. There are five species.

TERPSICHORE, in the mythology one of the Nine Muses.She precided over dancing.

TERRA, or THE EARTH , [Lat.] in the Copernican Systemis the third planet in order from the Sun . It is removed at theimmense distance of about 95 millions of miles from that lumi-nary, and revolves round him in 365 days, 5 hours, 48-J-f minutes,which is her tropical period, i. e. from one equinox, to the sameagain; but her sidereal and anomalistic revolutions are 365d. 6h.9m. Ilfs, and 365d. 6h. 14m. 37s. respectively. Her diameter isabout 7954 English miles, and her circumference about 25000:hut, if seen from the sun, she would appear under the very smallangle of 17" of a minute, as has been successfully demonstratedfrom numerous observations made on the two transits of Venus over the solar disk in 1761 and 1769. She turns round her axishi 23h. 56wi. 4s. but the natural day, or that made by the Sun ’s''eturn to the same point of the heavens, is 24 hours at a meanr ate. The place of her aphelion, (Jan. I, 1812,) is in VJ 9° 41'46",8, having a progressive motion of 13',32 in a year as it re-spects the stars, and of 63",65 in the same time as it regards theEquinox. She has no nodes, her annual path, styled the Ecliptic ,filing made by astronomers the standard by which the deviation ofjhe other planets therefrom are measured. The eccentricity ofher orbit is 1681 -jout of 100000 of those parts into which herdistance from the Sun is supposed to be divided ; and the greatestec luation of her orbit (Jan. 1, 1812,) 1° 55' 27",744, it having ana "nua! decrease of 0",188. For further particulars respecting thisplanet, see Astronomy. —That the Earth is not at rest in theCe "hc of the universe, as many have imagined, having all theCc frstial bodies moving round her in 24 hours, or thereabouts,■bay be proved from their vast distance, and also consequent su-P e rior magnitude. (See Astronomy.) The great distance of thebn from the Earth is so evident as hardly to need any demonslra-!° n ! for astronomers, in their calculations of the distance and’ Ze of the Sun proceed precisely upon the same principles as thegeometricians do in measuring the height of a tower and its dis-]pf C f fr° m 'he place of observation. For (Plate XXV. Fig. 11,)th s c ’ rcle of which C is the centre represent the Earth , ZPEB,

. e bun’s apparent quadrantic are while moving from the horizon

.'he zenith, and ** TS ***** the sphere of the fixed starsjf. ! c h is at an inconceivable distance from us. Then it is evident,j n ,, le buri be in P, and the observer at A, that he will see the Sun

the sphere of the’fixed stars at S, which is at the extremity of

VOL. iv.— no. 205 .

the line APS ; but it is also evident that another observer at thecentre of the Earth C, or, which is the same thing, at a placewhere the Sun is precisely in the zenith, must see the Sun at thealtitude PF in the sphere of the fixed stars at T, which is at theextremity of the line of vision CPT. The difference of thesetwo apparent places TS is the quantity of the solar parallax at thealtitude PF. But when the Sun is posited in the horizon AF*it is then the greatest of all, and is equivalent to the apparentsemidiameter of the Earth as seen from the Sun . So then, hav-ing this parallax, we can find the distance of the Sun by Trigo-nometry ; for having AC the semidiameter of the Earth , the angleFAC, which is a right one, and the angle AFC, the horizontalparallax, the distance of the Sun AF is readily obtained. SeeTrigonometry. Now if the solar parallax were not so exceed-ingly minute, as not even to equal 9 seconds, but amounted to aminute or two; this method of ascertaining it, and his consequentdistance from the Earth , would be sufficient. But as astronomicalinstruments cannot be had to that degree of perfection as to besure of the observation to the nicety of a second of a degree,astronomers have had recourse to the two last transits of the planetVenus over the Sun ’s disk for the resolution of this problem, andthey have succeeded in this matter almost to the utmost extent oftheir wishes; and from a comparison of the numerous observationsmade upon these phenomena they have demonstrated that theSun ’s horizontal parallax does very little, if at all, exceed 8"-^..Nor can the determination of so small an angle be subject to anymaterial error, but can be proved to be true to within ^feth partof the whole, from the nature of a transit of Venus over the solardisk ; for in this case we have not to measure the angle of theparallax by means of an instrument, but only the duration of thetransit. Now it is evident that if we suppose the Sun ’s distancefrom the Earth to be divided into 100000 parts that the distance ofVenus from the Earth must occupy 72333 of those parts, fromthe single circumstance of the greatest angle of her recess fromthe Sun being about 47°; consequently her parallax, when in herinferior conjunction, must be near four times as great as the Sun ’s.As this must make a very sensible difference in the phsenomenaof the transits, when viewed from different parts of the Earth ,astronomers were sent to the places where the effect of parallaxwould be the greatest of all; and in the transit of 1769 it was ob-served that Venus passed over the solar disk in a track upwards of20 seconds of a degree more to the north of his centre at Otahekethan she did at Wardhus, which occasioned the duration of thetransit to be 23m. 10s. shorter in the former place than in the latter,because at the former place the chord of description was longer,the planet being apparently nearer to the Sun ’s centre ; but in thelatter considerably shorter because the planet was apparently fur-ther removed from it. This is evident to any person who is ac-quainted with the nature of a circle. As in both cases, theplanet’s apparent motion would be the same, i. e. about 4 minutesof a degree per hour, the shorter chord must be described severalminutes sooner than the other. r l his difference of time in theduration of the transit of 1769 between the two interior contacts,that is to say, between the instant in which Venus was just en-tered entirely upon the Sun ’s disk, and the instant in which itbegan to go off, amounted at Wardhus and Otaheite , to not lessthan 23m. 10s. the duration at the former place being 5h. 53m.14s. and in the latter only 5b. 30m. 4s. From these observations,connected witli a great number of others, it is manifest that thehorizontal parallax of Venus is not greater than ; con-

sequently the horizontal solar parallax cannot be greater than8',62853 ; which proves that the Sun’s distance from the Earth cannot be less than 95 millions of English miles, as fully appearsfrom the following trigonometrical operation: As the sine of theangle AFT, (Plate CXXX1II. fig. 3,) or the Sun ’s horizontalparallax, is to the base AT, or the semidiameter of the Earth ;so is radius, to the bypothenuse TF, or the Sun ’s distance fromthe Earth ’s centre. But, to resolve this triangle with tolerableaccuracy by logarithms, it will be best to assume the angle AFTseveral times greater than it is; and as the horizontal parallaxincreases precisely in the same proportion as the distance decreases’to multiply the result of the proportion by the number of timesthe solar parallax is less than that for which the analogy is madeThus assuming the horizontal parallax 1 degree, proceed asfollows:

8 S

As