644 
EQU 
the poles is a circle, the poles of which coin- 
cide with the poles of tile ecliptic, and that 
the pole will move along that circle so very 
slowly, as to accomplish the whole revolu- 
tion in 25791 years nearly. The diameter 
oi this circle is equal to twice the inclination of 
the ecliptic to the equator, viz. to about 47°. 
Now, as the ecliptic is a fixed circle in the 
heavens ; but the equator, which must be equi- 
distant from the poles, moves with the poles; 
therefore the equator must be constantly 
changing its intersection with the ecliptic. 
And from the best observations it appears 
that the equator cuts the ecliptic every year 
50". 25 more to the westwards, than' it did 
»he year before : hence the sun’s arrival at the 
equinoctial point precedes its arrival at the 
same fixed spot of the heavens every vear bv 
20' 23" of time, or by an arc of 50". 25.' Thus, 
by little and little, these equinoctial points 
will cut the ecliptic more and more to the 
westward, until, after the long period of25 791 
years, they will cut it again at the same point 
precisely, 
I he 12 constellations, which, as has been 
mentioned in the preceding pages, occupy 
the whole of the zodiac, have given their 
names to 12 equal portions of the ecliptic, 
each portion consisting of 30° ; and each por- i 
tion was marked by the sign, mark, or cha- j 
racter, peculiar to^the constellation to which : 
it belonged, or with which it coincided, when 
the constellations were first noticed, at which 
time the vernal equinox took place in the 
constellation of Aries, the summer solstice in 
that of Cancer, &c. : but on account of the 
precession of the equinoxes, the constellations 
no longer coincide with those points ; for in- 
stance, the vernal equinox is in the constella- 
tion of Pisces, and the constellation of Aries is 
now considerably removed from it, and is gone 
nearer to the summer solstice ; and so are all 
the other constellations removed, yet their 
characters have been left to denote the same 
parts of the ecliptic ; thus the vernal equinox 
is cqlled the first point of Aries, and is marked 
<Y > ; and so of the rest. 
From what has been said above, it appears 
that not only the equinoctial points, but also 
the solstitial points, must change accord- 
ing 1 )'- 
EQUISETUM, horse-tail, a genus of the 
order ot Alices, in the cryptogamia class of 
plants, and in the natural method ranking 
under the 5 1st order, conifer ax There is a 
spike of peltated or shielded fructifications 
opening at the base. There are seven spe- 
cies, of which the most remarkable art* : 
1, The sylvaticum, or wood horse-tail. It 
grows in woods and moist shady places in 
many parts of England and Scotland. The 
stalk rises from 12 to 18 inches high, angu- 
lar, and rough to the touch ; the angles being 
edged with sharp spic ills', scarcely visible 
without a microscope. The leaves grow ver- 
ticillate, 12 or more in a whorl, and these 
whorls are about an inch distant from one 
another. The leaves are very slender, nearly 
quadrangular, about five inches long, pen- 
dent, and beset with several other secondary 
whorls, so that it resembles a pine-tree in mi- 
niature. Horses are very fond of this plant, 
and in some parts of Sweden it is collected 
to serve them as winter food. 
2. The arvense, common or corn horse- 
tail, grows in wet meadows and corn-fields. 
The most remarkable property of tins is, that 
E Q U 
its seeds, when viewed by a microscope, ore 
seen to leap about as if they were animated. 
It is a troublesome plant in pastures ; and dis- 
agreeable to cows, being never touched by 
them unless they are compelled by hunger, 
and then it brings on an incurable diarrhoea. 
It does not seem to affect horses or sheep. 
3. The palustne, marsh horse-tail, or pad- 
dock-pipe, is frequent in marshes and ditches. 
It is not so rough as the former, but is like- 
wise prejudicial to cattle. 
4. The iluviatile, or great river horse-tail, 
is frequent in shady marshes, and on the 
brinks of stagnant waters. It is the largest 
ot all the species, growing sometimes to the 
height of a yard, and near an inch in diame- 
ter. Haller tells us, that this kind of equise- 
tum was eaten by the Romans ; and Linnams 
affirms that oxen and rein-deer are fond of 
it, but that horses refuse it. 
5. The hyemale, rbugh horse-tail, shave- 
grass, or Dutch rushes. 'This is much used 
by the whitesmiths and cabinet-makers, un- 
der the name of Dutch rushes, for polishing 
their metals and wood. The fact is, that there 
is a portion of flint, which exists in this plant 
near the surface, in the form of very fine 
grains, which enables it to perform tins of- 
fice. All the other species will answer this 
purpose in some degree, but the last better 
than any of the rest. In Northumberland 
the dairy-maids scour and clean their milk- 
pails with it. Some imagine that if cows are 
fed with this species their teeth will fall out. 
EQLT1 Y, is a construction made by the 
judges, that cases out of the letter of a sta- 
tute, yet being within the same mischief or 
cause of making the same, shall be within the 
same remedy that the statute provides. And 
the reason is, that the lawmaker could not 
possibly set down all cases in express terms : 
thus, though it may be unlawful to kill a 
man, yet it is not unlawful for one to kill an- 
other assaulting him, in order to preserve his 
own life. 4 Inst. 24. 
Equity of redemptiGn on mort- 
gages. If where money is due on a mort- 
gage, the mortgagee is 'desirous to bar the 
equity of redemption, he may oblige the 
mortgagor either to pay the money, or be 
foreclosed of his equity, which is done by 
proceedings in the court of chancery. 
Equity also frequently signifies the court 
of chancery, where controversies are deter- 
mined which do not properly come under 
any express law. See Chancellor. 
EQUIVALENT, an appellation given to 
things which agree in nature, or other circum- 
stances, as force, virtue, &c. 
EQUIVOCAL TERMS or WORDS, 
among logicians, are those which have a 
doubtful or double meaning. 
According to Mr. Locke, the doubtfulness 
and uncertainty of words lias its cause more 
in the ideas themselves, than in any incapa- 
city of the words to signify them ; and might 
be avoided, would people always use the 
same term to denote the same idea, or col- 
lection of ideas : but, adds he, it is hard to 
find a discourse on any subject where this is 
the case ; a practice which can only be im- 
puted to folly, or great dishonesty: since a 
man, in making up his accompts, might with 
as much fairness use the numeral characters 
sometimes for one, sometimes for another col- 
lection of unities. 
EQU 
Equivocal generation, the produc- 
tion of animals without the intercourse be- 
tween the sexes, by the influence ot the sun 
or stars, &c. 4 he equivocal gentialion of 
plants, is their production without seed, in 
the ordinary course of nature. This kind of 
generation is now quite exploded by the 
learned. Mr. Ray is clearly of opinion that 
there is no such thing as spontaneous or 
equivocal generation, but that all animals are 
the issue oi parents of the same species with 
themselves; and with him agree Redi, i l- 
lughbv, and Lister. 4 his last author has 
fully refuted the vulgar notion, that horse- 
hairs thrown into water will become animated 
bodies ; by shewing that appearances of this 
kind are nair-worms bred m the bodies of 
other insects, and particularly of the common 
black-beetle. 
EQUULEUS, or ecuuleus, in antiquity, a 
kind of rack used for extorting a confession, 
at first chiefly practised on slaves, but after- 
wards made use of against the Christians. The 
equuleus was made of wood, having holes at 
certain distances, with a screw, by which the 
criminal was stretched to the third, some- 
times to the fourth or fifth holes, his arms 
and legs being fastened on the equuleus with 
cords ; and thus was hoisted aloft, and ex- 
tended in such a manner that all his bones 
were dislocated. In this state red-hot plates 
were applied to his body, and he was goaded 
in the sides with an instrument called lin- 
gula. 
Equuleus, in astronomy, a constellation 
of the northern hemisphere, whose stars, ac- 
cording- to Ptolemy and Tycho’s catalogues, 
are four, but in Mr. Flamsteed’s ten. 
EQU US, the horse, a genus of the mam- 
malia class, of the order of bell me. 4 he ge- 
neric character is, front teeth in the upper 
jaw six, parallel ; in the lower jaw six, some- 
what projecting ; canine teeth, one on each 
side, in both jaws, remote from the rest ; 
feet with undivided hoofs. 
1. Equus caballus, or the common horse, 
the most noble and interesting of quadru- 
peds, is supposed to be found in a state of 
nature in several parts of Asia and Africa. 
In this state it is smaller than the domestic 
or tame animal, with a larger head, a more 
arched forehead, and the body thickly cover- 
ed with pale-brown, or mouse-coloured hair. 
It has been affirmed by several authors, that 
wild horses were to be found in the deserts 
of Arabia ; but we must agree with Mons. 
Sonnini, in thinking it not very probable that 
this animal should be able to exist in such 
deserts. We must, therefore, rather sup- 
pose that it is occasionally found wild in some 
parts of the country bordering perhaps on 
the confines of the desert. It is certain that 
in Arabia the most beautiful domestic horses 
are bred ; and even those which are kept by 
the Arabs of the desert are allowed to excel 
most others in swiftness and elegance of 
form, and it is from their breed that the Eu- 
ropean horses have been gradually improved. 
See Plate Nat. Hist. fig. 182. 
Large herds of wild horses are said to be 
found about the lake Aral, near Kusneck, in 
lat. 54° ; on the river 4'om, in the southern 
parts of Siberia; and in the great Mongalian 
deserts, and among the Kalkas, north-west of 
China ; and it is affirmed that they will oc- 
casionally surround and trepan the horses of 
1 the Mongolians and Kalkas, while grazing. 
