G N A 
G N O 
809 
cases, to prevent t he necessity of drinking. 
Mr. Fuller, in his Medicina Gvmnastica, 
recommends this root as a very useful pec- 
toral; an assertion warranted by experience. 
An extract is directed to be made from it in 
the shops; yet this preparation is chiefly- 
brought from abroad, though the foreign ex- 
tract is not the best. 
G MELINA, a genus of the angiospermia 
order, in the didynamia class of plants, and 
in the natural method racking under the 40th 
order, personate. Thesfcalyx is nearly qua- 
dridentated; the corolla campanulated or 
bell-shaped; there are two bipartite and two 
simple anthers ; the fruit is a plum with a 
bilocular kernel. 1 here is one species, a tree 
of Malabar. 
G NAP GALIUM, cudzveed, goldi/ locks, 
eternal, flower, &e. a genus of the polygamia 
superflua order, in the svngenesia class of 
plants, and in the natural method ranking 
under the 49th order, composite. The re- 
ceptacle is naked ; the pappus feathered ; the 
calyx imbricated, with the marginal scales 
roundish, parched, and coloured. 1 here are 
-66 species; the mod remarkable of which 
are: 1. The margaritaceum, or pearly-white 
eternal ilower, has creeping, very spreading 
roots, crowned with broad, spear-shaped, 
■white, hoary leaves; herbaceous, thick, woolly 
stalks, a foot and a half high, branching out- 
ward, with long, acute-pointed, white, woolly 
leaves, and terminated by a corymbose cluster 
of yellowish flowers, which appear in June 
and July, and are very ornamental. 2. The 
plantaginium has large woolly radical leaves, 
decumbent running roots, and herbaceous 
simple stalks, rising six or eight inches, ter- 
minated by a cory.nbus of white flowers jn 
June, Julv, &c. 3. i lie stechas has a shrub- 
h\ stalk, dividing into slender branches three 
feet long, terminated, by corymbose clusters 
of s ellosv flowers, appearing in May and 
June. 4. 'Fhe orientale has three varieties, 
with yellow, gold-coloured, and white silvery 
flowers. They have shrubby stalks, rising 
lwo or three feet high. 5. The odoratissi- 
iriam, or sweet-scented eternal flower, has 
shrubby winged stalks, branching irregularly 
a \ ard high, with corymbose clusters ot bright- 
eellow flowers, changing to a dark yellow. 
6. 'i lie arboreiim, or tree gnaphalium, has a 
wooclv stem, branching four or five feet high, 
narrow sessile leaves, with revolute borders, 
smooth on their upper side, and roundish 
bunches of pale-yellow flowers. The first 
three soils are hardy, and will thrive in any 
soil or situation. 'The first two increase ex- 
ceedingly by their roots; and the third is 
easily propagated by slips. The fourth, fifth, 
and "sixth sorts are somewhat tender, and 
therefore should be kept in pots, to be shel- 
tered in a greenhouse or garden-frame in 
winter. Others may be planted in the full 
ground, in a dry and warm situation, espe- 
c ally the oriental kind and varieties, and 
like,' ise the sweet-scented kind ; for these tw . 
species will struggle tolerably through an or- 
dinary winter, and make a pretty appearance 
during the summer months, AH these are 
propagated by slips or cuttings of their shoots. 
The tlowers of all these species are remark- 
able for retaining their beauty for years, if 
carefully gathered in a dry day, soon after 
4,liey are blown. 
GNAT. -See Culex. 
GNEISS, in mineralogy, is composed es- 
sentially of felspar, quart/, and mica, forming 
plates which are laid on each other, and se- 
parated by thin layers of mica. It differs 
from granite in being shistose. Gneiss rocks 
are usually stratified., Like granite, it some- 
times contains shorl and garnet. r l he beds 
of gneiss sometimes alternate with layers of 
granular limestone, shistose, hornblende, and 
porphyry. It is rich in ores, almoit every 
metal having been found in gneiss rocks, 
either in veins or beds. 
GNETUM, a genus of the monadelphia 
order, in the monoecia class of plants. The 
amentum of the male is a single scale ; there 
is no corolla, and but one filament with a 
pair of anthenr. The calyx of the female is 
of the same form; there is no corolla; the style 
with the stigma is trifid; the fruit a mono- 
spermous plum. There is one species, a herb 
of the East Indies. 
GNEDIA, a genus of the monogynia order, 
in the octandria class of plants. 'I he calyx 
is funnel-shaped and quadrilid, with four pe- 
tals inserted into it; there is one seed some- 
what resembling a berry. There are 11 spe- 
cies, shrubs of the Cape. 
GNOMON, in dialling, the style, pin, or 
cock of a dial, which by its shadow shews the 
hour of the day. The gnomon of every dial 
represents the axis of the world. See Dial 
and Dialling. 
Gnomon, in geometry. If in a parallelo- 
gram A BCD (plate Miseeh fig. 103.) the 
diameter AC be drawn; also two lines EE, 
II T, parallel to the sides of the parallelo- 
gram, and cutting the diameter in one and 
the same point G, so that the parallelogram 
is, by these parallels, divided into four pa- 
rallelograms, then are the two parallelograms 
DG, BG, through which the diameter does 
not pass, called complements; those through 
which the diameter passes, EH, El, are called 
the parallelograms about the diameter; and a 
gnomon consists of the two complements, and 
either of the parallelograms about the diame- 
ter, viz. G D + HE + E I, or G D -f FI -f 
G B. 
Gnomon, in astronomy, a style erected 
perpendicular to the horizon, in order to find 
the altitude of the sun. Thus, in the right- 
angled triangle ABC, fig. 104., are given 
A B the length of the style, BC the length of 
its shadow, and the right angle A BC. Hence, 
making C B the radius, we have this analogy 
for finding the angle AC B, the sun’s altitude, 
viz. BC : A B : : radius : tangent of the angle 
C. By means of a gnomon, the sun’s meri- 
dian altitude, and consequently the latitude 
of the place, may be found more exactly than 
with the smaller quadrants. See Quadrant. 
By the same instrument the height of any 
object G 11 may be found; for as DF (fig. 
10 j) the distance of the observer’s eye from 
the gnomon, is to DE, the height of the style, 
so is K II, the distance of the observer’s eye 
from the object, to G II its height. 
The following example will serve to illus- 
trate the above proposition. Pliny says, that 
at Home, at the time of the equinoxes, the 
shadow is to the gnomon as 8 to 9 ; there- 
9 
fore as 8 : 9 : : l or radius : — — l' 125 a tan- 
gent, to which answers the angle 48° 22', 
which is the height of the equator at Rome, 
and its complement 41° 38' is therefore the 
GOB 
height of the pole, or the latitude of tha 
plice. 
Riccioli remarks the following defects in 
the observations of the sun’s height, made 
with the gnomon by the antients, and some 
of the moderns, viz" that they neglected the 
sun’s parallax, which makes his apparent alti- 
tude less, by the quantity of the parallax, 
than it would be if the gnomon were placed 
at the centre of the earth: 2d, they neglect- 
ed also the refraction, by which the apparent 
height of the sun is a little increased : and 
3dly, they made the calculations from the 
length of the shadow, as if it were terminated 
l)y a ray coining from the centre ot the sun’s 
disc, whereas the shadow is really terminated 
by a ray coining from the upper edge ot the 
sun’s disc ; so that, instead ot the height of the 
sun’s centre, their calculations gave the 
height of the upper edge of his disc: and, 
therefore, to the altitude of the sun found by 
the gnomon, the sun’s parallax must be add- 
ed, and from the sum must be subtracted 
the sun’s semidiameter, and refraction, which 
is different at different altitudes; which being 
done, the correct height of the equator at 
Rome will be 4S° 4' h", the complement of 
which, or 41° 55' 46", is the latitude. 
Idle preceding problem may be resolved 
more accurately by means of a ray et light 
let in through a small hole, than by a shadow, 
thus: make a circular perforation in a brass 
plate EF (fig. 106.) to transmit enough of 
the sun’s rays to exhibit his image on the 
floor, or a stage; fix the plate parallel to the 
horizon in a high place, proper for observa- 
tion, the height of which above the tloor let 
be accurately measured with a plummet. Let 
the floor, or stage, be perfectly plane and 
horizontal, and coloured over with some white 
substance, to shew the sun more distinctly . 
Up on this horizontal plane draw a meridian 
line passing through the foot or the centre of 
the gnomon, AG, i. e. the point upon which 
the plummet falls from the centre of the hole; 
and upon this line note the extreme points I 
and K of the sun’s image or diameter, and 
from each end subtract the image of half th<# 
diameter of the aperture, viz. R 11 and Li; 
then will H E be the image of the sun’s dia- 
meter, which, when bisected in B, gives the 
point on which the rays fall from the centra 
of the sun. 
Now having given the line AB, and the 
altitude of the gnomon AG, besides the right 
angle A, the angle B, or the apparent altitude 
of the sun’s centre, is easily found, thus: as. 
A B : A G : : radius : tang, angle B. 
GNOSTICS, in church-history, Christians 
so called, it being a name which almost all the 
antient heretics affected to take to express 
that new knowledge and extraordinary light 
to which they made pretensions; the word 
gnostic signifying a learned or enlightened 
person. 
GOA F. See Capra. 
Goat-sucker. See Caprimui.cus. 
GOB1US, Goby, in ichthyology, a genus 
of fishes belonging to the order of thoracici. 
The generic character is, head small ; eves 
approximated ; gill-membrane four-rayed ; 
ventral fins united into the form of a funnel. 
There are eight species, of which the follow- 
ing are the principal. 
1. Gobius nicer. Common goby. This spe- 
cies grows to the length of six inches ; th« 
