TIU 
head, and its pods tetraspermous. It is 
very common in fields and pastures. It is 
well known to be excellent fodder for cat- 
tle : and the leaves are a good rustic hy^ 
grometer, as they are always relaxed and 
flaccid in dry weather, but erect in moist or 
rainy. T. pratense, purple or red cloyer, 
is distinguished by densg spikes, unequal cO: 
rollas, by bearded stipulas, ascending stalks, 
and by the calyx having four equal teeth. 
The red clover is common in meadows and 
pastures, and is the species which is gene- 
rally cultivated as food for cattle. It 
abounds in every part of Europe, in North 
America, and even in Siberia. It delights 
most in rich, moist, and sunny places, yet 
flourishes in those that are dry, barren, and 
shady. See Husbandry. 
TRIGLA, the gurnard, in natural history, 
a genus of fishes of the order Thoracici. 
Generic character : head large, mailed, and 
marked yvith rough lines; eyes large; nos- 
trils double; gill covers spiny; gill mem- 
brane seven-rayed ; before the pectoral fins 
of most species there are articulate proces- 
ses, somewhat like fingers. There are four- 
teen species. T. gurnardus, or the grey 
gurnard, varies in length from one to two 
feet ; feeds on worms and insects ; inhabits 
the seas of Europe, and the coasts of this 
island, and is considered by many as excel- 
lent for the table, though generally not in 
high estimation. T. volitans, or the flying 
gurnard, is found in the Indian, Atlantic, 
and Mediterranean seas. It is about a foot 
in length, and its pectoral fins are of an ex- 
traordinary size, and great transparency. 
By these it is enabled to sustain short flights . 
out of the water, when hardly pressed by its 
various enemies. 
TRIGLOCHIN, in botany, arrow-grass, 
a genus of the HexandriaTrigynia class and 
order. Natural order of Tripetaloideae. 
Junci, Jussieu. Essential character : calyx 
three-leaved; petals three, calyx form ; 
style none ; capsule opening at the base. 
There are three species. 
TRIGONELLA, in botany, fenu-^reek, 
a genus of the Diadelphia Decandria class 
and order. Natural order of Papilionacem 
or Leguminosse. Essential character : ban- 
ner and wings nearly equal, spreading in 
form of a three-petalled corolla. There are 
twelve species. 
TRIGONIA, in botany, a genus of the 
Diadelphia Decandria class and order. 
Natural order of Malpighi®, Jussieu. Es- 
sential character: calyx five-parted; petals 
five, unequal, uppermost foveolate at the 
TRI 
base withhi ; nectary, two scales at the base 
of ‘the germ; filaments, some barren; cap- 
sule leguminose, three-cornered, three-cel- 
led, ihree-valved. There are two species : 
viz. T, vfflosa, and T, l®vis; both natives of 
South America, 
TRIGONOMETRY. The business of 
this important science is to find the angles 
where the sides are given ; and the sides, 
of their respective ratios, vfhen the angles 
are given; and to find sides and angles, 
when sides and angles are partly given. To 
effect this, it is necessary not only that the 
peripheries of circles, but also certain right 
lines in and about circles, be supposed 
divided into certain numbers of parts. The 
ancients, feeling tlie necessity of such a 
pre-division, portioned the circle into o6Q 
equal parts, which they called degrees ; 
each degree was again divided into 60 equal 
parts, called minutes; and each minute 
comprised 60 equal parts, called seconds. 
The moderns have improved upon thte divi- 
sion by the addition of anonius, or vernier, 
which may be carried to any extent, but is 
usually limited to decimating the seconds; 
noting each tenth part thereof. It vyould 
have been found a considerable convenience 
in mathematics, if the circle had been di- 
vided into centisimal parts, particularly in 
trigonometrical operations; thus making 
every quadrant to consist of 100 degrees, 
each degree of 100 minutes, and each mi- 
nute of 100 seconds : there can, indeed, be 
no doubt but all the arithmetical calcula- 
tions relating to the periphery, as well as 
to the secants, sinqs, tangents, radii, chords, 
and complements, would by this reforma- 
tion have been simplified. 
We shall be brief on tliis head, because it 
would require more space than could be 
allotted to any one branch of science, were 
we to follow the whole extent of trigono- 
metry in this place. The following defini- 
tions will be found useful: 1. The comple- 
ment of an arc is the difference thereof 
from a quadrant ; thus, if an arc measures 
60“, the complement is 30". 2. A chord, 
or subtense, is a right line drawn from one 
to the other end of an arc. 3. The sine, or 
right sine, of an arc, is a perpendicular fall- 
ing from one end of an arc to the radius 
drawn, at right angles thereto, towards the 
ether end of the arc. Hence it is clear that 
an arc of fiO” must have its secant, its radius, 
and its chord, all of the same length, form- 
ing an equilateral triangle. The secant and 
radius both proceed from the centre, but 
all sines are parallel to a vertical line pass- 
