324 H E L 
England; they fucceeded, produced flowers and ripe 
feeds during feveral years in the Chelfea garden. 
HELIOCEN'TRIC,orHELiQCEN'TRic Ah, adj. [from 
■ mAioj, Gr. the fun, and mwpov, a centre.] Belonging to 
that point in the ecliptic in which a (tar or planet would 
appear if feen from the fun. 
Heliocentric Place of a Planet, the place in 
which a planet would appear to be when viewed from 
the fun ; or that point of the ecliptic in which a planet 
viewed from the fun would appear to be : and therefore 
the heliocentric place coincides with the longitude of a 
planet viewed from the fun. 
Heliocentric Latitude of a Plan'et, the incli¬ 
nation of the line drawn between the centre of the fun 
and the centre of a planet, to the place of the ecliptic. 
The greateft heliocentric latitude is equal to the inclina¬ 
tion of the planet’s orbit to the plilne of the ecliptic. 
HELIOCOME'TES, f. A phenomenon fo me times 1 
obferved at the fetting of the fun, confiding of a large 
column of light, fixed or hung to that luminary, and 
drawing after it at its fetting, like the tail of a comet. 
HELIGDO'RUS, a native of Emefa in Phoenicia, and 
bifliop ol Trica in Theflaly ; flourifhed under tne em¬ 
perors Theodofius and Arcadius, at the clofe of the 
fourth century. In his youth he compofed a romance 
in the Greek language, entitled ALthiopica, reciting the 
loves of Theagenes and Chariclea. It is an ingenious 
and pleafing compofitjon, and has ferved as a modpl ifor 
fubfequent works of a like kind. A manufcript of this 
piece was faved by a foldier at the fack of Buda, and 
was printed at Bafil in 1534. A translation of it was 
made by a Polifh knight; and an edition of both, with 
the learned notes of Bourdelot, was printed at Paris in 
161 g, 8vo. 
HELIODO'RUS of Larissa, a Greek mathemati¬ 
cian, who flourifiied in the reign of the emperor Tibe¬ 
rius. He was the author of a treatife on optics, of which 
a fragment was publiflied at Florence, in Greek and 
Latin, 1573, 4to. and an Italian tranfiation of the fame 
by Ignatius Danti, with his edition of Euclid’s Optics. 
The fame piece was infected by Dr. Thomas Gale, in 
his OpuJ'cula Mythologica. But the mo it complete edition 
©f Heliodorus’s Optics was' publifhed at Paris, in Greek 
and Latin, in 1657,440. with notes by Bartholin. Among 
the manufcripts of Iliiac Voflius was a Treatife onWeights 
and Mealures, fuppofed to be written by this author. 
HELJOGAB'ALUS, a profligate Roman emperor. 
See the article Rome. 
HELIOGRAPH'IC,. adj. Pertaining to. the defcrip- 
tion of the fun. 
HELIOG'R APHY, f [from uAios, Gr. the fun, and 
y%a.<pa, to defcribe.] A defCription of the fun. 
HELIOM'ETER, J. An inftrument for meafuring 
the diameters of the fun, moon, and liars. It was in¬ 
vented by. M. Bouguer, in 1747 ; and is a kind of te- 
lefcope, confiding of two object-glafles of equal focal 
diftance, placed by the fide of each other, fo that the 
fame eye-glafs ferves for both. The tube, of this inftru- 
ment is of a conical form, larger at the upper end, which 
receives the two. objeit-glufies, than at the lower,.which 
is furniflred with an eye-glafs and micrometer. By the 
conftrudtion of this mfirument twodiflunSl images of an 
object are formed in the fpcus of The ey e-glafs, whofe 
diltance, depending on that of the two objeft-glafles 
from one another, may be meafured w ith great accu¬ 
racy. Mr. Savery di(covered a fimilar method of im¬ 
proving the micrometer, which was communicated to 
the Royal, Society in 1743, 
HELIOPH' lLA,f [iVom.»Ki,os # Gr. the fun, and piAo;., 
a friend; thefe plants being fond of fun-fliine.] In bo¬ 
tany, a genus of t he clafs tetradynamia, order (iliquofa, 
natural order of filiquofas, (cruciferae, JvJjf.) The generic 
characters are—Calyx: perianthium four-leaved ; leaflets 
fpreading, oblong, concave, membranaceous at the edge, 
deciduous; the two outer ones.bladdery at the bale. 
Corolla: four-petalled, cruciform; petals roundifh, flat, 
HE & 
feflile ; neftaries tvvo from the receptacle, bowed back to- 
wards the bladder of the calyx. Stamina: filaments fix, 
awl-fhaped, ereft, the length of the calyx, tw>o oppofite 
a little fliorter ; antherae oblong, ereiSl. Piftillum : germ 
cylindric; ftyle fliorter than the germ; ftigina blunt. 
Pericarpium : filique columnar, fomewhat torulofe, mu. 
cronate, two-celled, two-valved. Seeds: feveral.— EJfen~ 
tial Char after. NeClaries two, bowed back towards the 
bladder of the calyx. 
Species. 1. Heliophila integrifplia, or whole-leaved 
heliophila: leaves lanceolate, undivided. Stalk erecl, 
four or five, inches high, fending out two or three fide- 
branches. Leaves rough with hairs on the upper fur- 
face, ifmooth underneath.. The flowers grow in a loofe 
terminating bunch, and have no fcent. The corolla 
refembles that of .flax, or Anagallis monelli; is blue, 
and clofes at night. The pods are near three inches 
long, taper, and contain a double row of flat feeds. 
2. Heliophila coronopifolia, or buck’s-horn-leaved he¬ 
liophila: leaves linear, pinnatifid. This is a fmooth . 
plant. It grows about the fame height with the other, 
but branches more. The flowers are like thofe of the 
foregoing, coming out from June to October. 
3. Heliophila amplexjcaulis : leaves ftem-elafping, en¬ 
tire, fmooth ; filiques necklace-fhaped. Found at the 
Cape of Good Hope,, with niofl: of the other forts, by 
Thunberg, « 
4. Heliophila incana, or hoary heliophila: leaves fpa- 
tulate, quite entire, pubefcent; filiques villofe. Shrub-, 
by; flowering in May and Augufl. 
5. Heliophila ftliformis, or divaricated heliophila : 
leaves fubulate, filiform, fmooth; filiques pendulous; 
branches divaricate. Annual. Stem half a foot high, 
herbaceous, rufliy ; branches upright, fliorter. It flow¬ 
ers in July and Augufl.. 
6. Heliophila pu(ilia, or dwarf heliophila : leaves li¬ 
near; filiques necklace-fhaped, upright. Annual. A 
fpan high, upright, branched. 
7. Heliophila' flava: leaves linear; ftems flirubby, 
rufliy. Shrubby, having the appearance of broom, up¬ 
right, fparingly branched, fliff. It is doubtful whether 
this be a natural fpecies of this genus. 
8. Heliophila circaeoides: leaves cordate. It is de-. 
fcribed by Thunberg, under the name of Ghamiracornuta* 
9. Heliophila digitata : leaves palmate-pinnatifid, vil¬ 
lofe ; pinnas linear. The Item thickens very much up¬ 
wards, which gives this plant a Angular appearance. 
10.. Heliophila pinnata : leaves trifid and pinnate; 
leaflets linear ; filiques necklace-fhaped, upright. This 
refembles the fixth fpecies very much, but it has branch¬ 
ed or pinnate leaves. 
Propagation- and Culture. The feeds may be fown in the 
fpring on a fouth border, and when the plants come up,, 
if they are thinned and kept clean from weeds, it is all 
the culture they require. They are all natives of the 
Cape. 
HELIOPHO'BI,. a name given to.the white negroes. 
or albinos, from their natural averfion to the light of 
the fun. 1 See the article Albinos, vol. i. p. 240, and 
the correfpondent engraving. 
HELIOP'OLIS, or Aven, mentioned by Ezek. xxx. 
17. and called by Mofes On, and' in Jeremiah Bethfemes ; 
a city of Egypt, to the fouth-eaft of the Delta, and eaft, 
of Memphis ; where flood the temple of the fun, held in 
religious veneration. It gave name to th e Nomos Helio- 
polites. See the article Egypt, vol. vi. p. 363.—There 
was another Heliopolis in Coelofyria,, near the l'prings of, 
the Orontes; io called from the wor/hip of the fun,, 
which prevailed over all Syria. 
HE'LIOS, [Greek.] In mythology, the fon of Ccelus 
and Veda; the Sun. 
HE'LIOS COPE, yi A telefcope peculiarly adapted for 
viewing and obferving the fun without affeiSting the eye.. 
There are various kinds of them, ufually made by em¬ 
ploying coloured glafs for the objedt or eye-glafs, or both. 
The fame purpole is effected by a piece of. glafs blacked. 
