- @n that account 
HEL 
ratified by pofterity. - This event happened in the year 222, _ 
after a reign of three years and three quarters. Gibbon. 
HELIOMETER, formed of sjas:, fun, and ydlew, J mea- 
Jure, the name of an inftrument called alfo a/i-ometer, invented 
by M. Bouguer in 1747, for meafuring with particular 
exacétnefs the diameters of the ftars, and efpecially thofe of 
the fun and moon 
This inftrument is a kind of telefcope, confifting of two ~ 
object-glaffes, of equal focal diftance, placed one of t 
by fi 
the fide of the other, fo that the fame eyesglafs ferves 
for both. The tu 
largerat the upper end, which receives the two object- 
glaffes, than the lower, which is furnifhed with an 
glafs and micrometer. By the conftruétion. of this 
inftrument, two diftin& ject are formed 
ges of a 
in the focus of the eye-glafs, whofe diftance, depending 
on that of the two object-glaffes from one another, m 
may be eafily computed, by their pofition with refpe& 
to one another: for, if the ob 
n .are made in 
cover one another, pial which is common 
und, and; 
‘ to be larger than they 
By a to this initrument, pro- 
vided it be 4 a moderate length, M. Bouguer thought 
it very poffible to meafure angles of three or four 
yi aig which is of particular confequence in taking the 
diitance of ftars from the moon. With this inftrument 
are imagined 
{mall addition 
; al 
of the fun’s difk. 
are not fo equ as the other parts; on this 
account his image appears fomewhat extended in t 
ical direction. This is owing to t decompofition 
of light, which is known to confit of rays differently 
frangible in its paflage through our atmofphere. u 
the blue and violet rays, which proceed from t 
e 
point; fo that the vertical diameter is extended, or ap- 
pears longer than the horizontal diameter, Mem. 
Mr. Servington Savery difcovered a fimilar method of 
proving the mi » which was communicated ta the 
Royal Society in 1743. See Micromerer. 
OPHILA, in Botany, from saris, the Jun, and 
Gires, a eet becaufe this genus thrives more Particularly 
in un-fhine. It was fo named by profeffor Burmann, 
flava, ta 
folia, digitata and circeoide 
Acad, 
HEL 
Ve: Ze 3095" Juli, - Illut 
t. 563: (Chamira; Thunb. Nov. Gen. 48.)—Clafs and 
Siliquofae Nat. Ord. Sikguofe, Linn, 
four fpreading. leaves, oblong, 
at the margin, deciduous; the 
of 
the calyx. Stam. Filaments fix, awl- ed, ere¢t, a lon 
as i‘ calyx, two oppofite a little fhorter ; anthers oblong, 
erect, fT] 
than the germen ; ftigma obtufe. 
what torulofe, pointed, of two cells and two valves, Seeds 
an ‘ 
many. 
~ Eff. Ch. Neétaries two, bent back towards the veficular 
bafe of the calyx. = 
Profeffor Martyn, in his edition of Miller’s DiGionary, 
has enumerated ten {pecies of Heliophila, and Willdenow has 
defcribed twelve. They are all natives of the ape of 
- 926. Jacq. Ic. Rar. v. g. 
: undivided.’’—Native of 
ftony, uncultivated 
Leaves more or lefs h 
Calyx-veficles ph s. Linneus has remarked in 
Mamifi, that the corolia is blue, fhutting at night, like flax. 
Root annual. Stem round 
upper ones alternate, fhorter. 
with flender hairs. Calyx yellowith. Petals of a deep blue 
Seed brownifh. 
The other fpecies known are H. incana, amplexicaulisy 
a, eanefcens, puflla, filiformis, pendula, pinnata, co t= 
gata pi The laft is Thonberg’s Cha- 
mira cornuta, and is remarkable among its congeners for 
broad heart-fhaped leaves. : 
ELIOPOLIS, or The City af the Sun, in Ancient Geo- 
name of Mnevis, as he was at Me : 
Apis. There was alfo in this city another magnificent tem- 
Rome ; another has 
€ . 
them is ftill ftanding 
