$54 K E I, 
heiresses, or rather, in legal expression, co- 
heir:;. The o lienee of stealing an heiress is 
founded on the statute 3 Hen. YU. c. 2. 
\vhich enacts, that if any man shall, for lucre, 
take any woman, being maid, widow, or 
wife, and having substance either in goods 
or lands, or being heir apparent to her an- 
cestor, contrary to her will, and afterwards 
she be married to such misdoer, or by his 
consent to another, or deliled ; he, his pro- 
curers, and abbettors, and such as knowingly 
receive such woman, shall be deemed princi- 
pal felons; and by 39 Elia. c. 9. the benefit 
of clergy is taken away from principals, pro- 
curers, and accessaries before. And it is not 
material whether a woman so taken contrary 
to her will, be at last married or defiled with 
her own consent or not, if she were under the 
force at the time. 
IIeir-looms, are such goods and personal 
chatties as, contrary to tiie nature of chatties, 
shall go by special custom to the heir, along 
with the inheritance, and not the executor 
of the last proprietor. 
HEISTERLA, a genus of the monogvnia 
■order, in the decandria ciass of plants, and in 
the natural method ranking under the 12th 
order, lioloraeeax The calyx is quinquefid, 
the petals five ; the fruit is a plum on a very 
large-coloured calyx. There is one species, 
a tree of Martinico. 
IiELENIUM, bastard sun-flower, a ge- 
nus of the polygamia super;! ua order, in the 
svngenesia class of plants, and in the natural 
method ranking under the 49th order, com- 
positae. The receptacle is naked in the 
middle ; under the radius, paleaceous ; the 
pappus consists of five short awns; the calyx 
is simple and multipartite ; the florets of tiie 
radius semitrifid. The species are : 1 . The 
autunmale, with spear-shaped narrow leaves. 
2. The pubescens, with pointed, spear- 
shaped, sawed leaves. Both these are na- 
tives of North America, where they grow 
wild in great plenty. They rise to the height 
of seven or eight feet in good ground. The 
roots, when large, send up a great number of 
stalks, which branch toward the top; the 
uppar part of the stalk sustains one yellow 
flower, shaped like the sun-flower, but* much 
smaller, having long rays, which are jagged 
pretty deep into four or five segments. These 
plants may be propagated by seeds, or by 
parting their roots; the latter is generally 
practised in this country. The best season 
to transplant and part the old roots is in Oc- 
tober, when their leaves are past, or in the 
beginning of March just before they begin to 
shoot. They delight in a soil rather moist 
than dry, provided it is not too strong, or 
does not hold the wet in winter. 
HELEPOL1S, in the antient art of war, 
a machine for battering down the walls of a 
place besieged, the invention of which is as- 
cribed to Demetrius, the Poliorcete. Dio- 
dorus Siculus says, that each side of the he- 
lepolis was 405 cubits broad, and 90 in height; 
that it had nine stages, anti was carried on 
four strong solid wheels- eight cubits in dia- 
meter; that it was armed with large batter- 
ing-rams, and had two roofs capable of sup- 
porting them; that in the lower stages there 
were different sorts of engines for casting 
stones ; and in the middle they had large ca- 
tapultas for lancing arrows, and smaller in 
those above, with a number of expert men 
for working ail these machines. 
HU 
HE ELEA, in Grecian antiquity, was the 
greatest and most frequented court in Athens, 
for the trial of civil affairs. The judges who 
sat in it were at least fifty, but the more 
usual number was either two or five hun- 
dred. When causes of great moment were 
to be tried, it was customary to call in the 
judges of the other courts: sometimes a thou- 
sand were called in, and then two courts are 
said to have been joined: sometimes fifteen j 
hundred or two thousand were called in, and 
then three or four courts met together. They 
had cognizance of civil affairs of the greatest 
weight and importance, and were not per- 
mitted to give judgment till they had taken 
a solemn oath to do it with impartiality, and 
to give sentence according to the laws, &c. 
HELIACAL, in astronomy, a term ap- 
plied to the rising or setting of the stars, or, 
more strictly speaking, to their emersion out 
of and immersion into the rays and superior, 
splendor of the sun. 
A star is said to rise heliacally, when after 
having been in conjunction with the sun, and 
on that account invisible, it comes to be at 
such a distance from him, as to be seen in j 
the morning before sun-rising; the sun, by | 
his apparent motion, receding from the star j 
towards the east: on the contrary, the helia- 
cal settmg is when the sun approaches so near 
a star as to hide it with his beams, which pre- 
vent the fainter light of the star from being 
perceived, so that the terms apparition and 
occultation would be more proper than ris- 
ing and setting. 
All the fixed stars in the zodiac, as also 
the superior planets, Mars, Jupiter, and Sa- 
turn, rise heliacally in the morning, a little 
before sun-rising, and a few days after they 
have set cosmically. Again, they set helia- 
cally in the evening, a short time before 
their achronycal setting. But the moon, 
whose motion .eastward is always quicker 
than the apparent motion of the sun, rises 
heliacally in the evening, after the new moon, 
and sets heliacally i nr the morning, when old 
and approaching to a conjunction with the 
sun. 
The inferior planets, Venus and Mercury, 
which sometimes seem to go westward from 
the sun, and sometimes again have a quicker 
motion eastward, rise heliacally in the morn- 
ing, when they are retrograde; but vrhen 
direct in their motions, they rise heliacally 
in the evening. The heliacal rising or set- 
ting of the moon happens when she is 17° 
degrees distant from the sun ; but for the 
other planets 20° are required ; and for the 
fixed stars more or less according to their 
magnitude. 
IIELIANTHUS, the great sunflower, a 
genus of the polygamia frustanea order, in 
the syngenesia class of plants, and in the na- 
tural method ranking under the 49th order, 
compositae. The receptacle x is paleaceous 
and plane; the pappus diphyllous ; the calyx 
imbricated; the scales standing a little out at. 
at the tops. There are 12 species, most of 
which are now very common in our gardens, 
though all of them are natives of America, 
f hey are all very hardy, and will thrive in 
almost any soil or situation. They may be 
propagated either by seeds or by parting 
their roots, but most of them are annual. The 
Jerusalem artichoke belongs to this genus. 
HELICOID parabola, or the parabolic 
. spiral, is a curve arising from the supposi- 
H F, L 
tion that the common or Apollonian para- 
bola is bent or twisted, till the axis .come into 
the periphery of a circle, the ordinates still 
retaining their places and perpendicular po- 
sitions with respect to the circle, all these 
lines still remaining in the same plane. Thus, 
the axis of a parabola being bent into the 
circumference BCDM (Plate Miscell. fig. 
119-), and the ordinates CF, DG, &c. still 
perpendicular to it, thou the parabola itself, 
passing through the extremities of the ordi- 
nates, is twisted into the'eurve BEG, Ac. 
called the helicoid, or parabolic spiral. 
Hence all the ordinates CF, DG, &c. tend 
to the centre of the circle, being perpendi- 
cular to the circumference. 
Also, the equation of the curve remains the 
same as when it was a parabola; viz. putting 
x = any circular absciss BC, and y = CE 
the corresponding ordinate, then is px = >, -, 
where p is the parameter of the parabola. 
HELICON 1A, a genus of the mcnogynla 
order, in the pentandria class of plants. The 
spatha is universal and partial ; there is no 
calyx; the corolla has three petals, and the 
nectarium two leaves ; the capsule is three- 
grained. T here are three species, beautiful 
herbaceous stove plants from South America 
and the West Indies. 
HELICTERES, the screw-tree , a genus 
of the decandria order, in the gynandria c lass 
of plants, and in the natural method ranking 
under the 37th order, columniferse. T he 
calyx is monophyllous and oblique ; there 
are live petals, and tiie nectarium consists of 
five petal-like leaflets; the capsules are in- 
torted or twisted inwards. There are nine 
species, all nat ives of warm climates. They 
are shrubby plants, rising from rive to four- 
teen feet in height, adorned with flow ers of a 
yellow colour. They are propagated by 
seeds, but are tender, and in this country 
must be kept in a stove during the winter. 
HELIOCAR IT S, a genus of the digynia 
order, in the dodecandria class of plants, and 
in the natural method ranking under the 37th 
order, columnifene. T he calyx is tetraphyl- 
lous; the petals four; the styles simple; the 
capsule bilocular, compressed, and radiated 
lengthwise on each side. There is one spe- 
cies, a tree of La Vera Cruz. 
HELIOCENTRIC latitude of a planet, 
the inclination of a line drawn between th« 
centre of the sun and the centre of a pla- 
net, to the plane of the ecliptic, which may 
be thus determined. 
If the circle FGH (Plate Miscell. rig. 121.) 
represent the orbit of tiie earth round the 
sun, and the inner one AN Bn, be so placed 
as to incline to the plane of the other (on 
which account it appears in the form of an 
ellipsis), then when the planet' is in the node 
n, it will appear in the ecliptic, and so have 
no latitude. But if it move to P, then, being 
seen from the sun, it will appear to decline 
from the ecliptic, or to have latitude; and 
the inclination of the line SP to the plane of 
the ecliptic, is called the planet’s heliocentric 
latitude; the measure of which is the angle 
PS p, supposing the line P p to be perpendi- 
cular to the plane of the ecliptic. 
This heliocentric latitude will be continu- 
ally increasing till the planet come to the 
point A, which they call the limit or utmost 
extent of it; and then it will decrease again 
till it reach the other node N, when it will 
