RUD 
the Tetraiidria Monogynia class and order. 
Natural order of Stellatae. Rubiaceas, Jus- 
sieu. Essential character : corolla one-petal- 
led, bell-shaped; berries two, one-seeded. 
There are seven species. See Mabder. 
RUBRIC, in the canon-law, signifies a 
title or article in certain ancient law-books ; 
thus called because written, as the titles of 
the chapters in our ancient Bibles are, in 
red letters. Rubrics also denote the rules 
and directions given at the beginning, and 
in the course of, the liturgy, for the order 
and manner in which the several parts of 
the office are to be performed. There are 
general rubrics and special rubrics, a rubric 
for the communion, &c. In the Romish 
missal and breviary are rubrics for matins, 
for lauds, for translations, beatifications, 
commemorations, &c. 
RUBUS, in botany, the raspberry, a 
genus of the Icosandria Polygynia class and 
order. Natural order of Senticosse. Ro- 
saceae, Jussieu. Essential character ; calyx 
five-cleft: petals five; berry composed of 
one-seeded acini. - There are thirty-two 
species ; among which is the R. idaeus, or 
common garden raspberry, too well known 
to need a particular description : it is found 
wild in many parts of Europe, particularly 
in rocky mountains, moist situations, woods, 
and hedges. The varieties of the raspberry 
are, the red-fruited, the white-fruited, and 
the twice-bearing. 
RUBY. See Corundum. 
Ruby, in heraldry, denotes the red co- 
lour wherewith the arms of noblemen are 
blazoned ; being the same which in the arms 
of others, not noble, is called gules. 
RUDBECKIA, in botany, so named 
from Olaus Rudbeck, fatlier and son, pro- 
fessors of botany at Upsal, a genus of the 
Syngenesis Polygamia Frustranea class and 
order. Natural order of Composite Op- 
positifolte. Corymbiferae, Jussieu. Essen- 
tial character : calyx with a double row of 
scales; crown of the seed a four- toothed 
rim; receptacle chaflFy, conical. There 
are seven species. 
RUDDER, in navigation, a piece of tim- 
ber taming on hinges in the stern of the 
ship, and which, opposing sometimes one 
side to the water and sometimes another, 
turns or directs the vessel this way or that. 
The rudder of a ship is a piece of timber 
hung (w the stern posts by four or five iron- 
hooks, called pintles, serving as it were for 
the bridle of a ship to turn her about at the 
pleasure of the steersman. The rudder 
being perpendicular; and without-side the 
RUL 
ship, another piece of timber is fitted to it 
at right angles, which comes into the ship, 
by which the rudder is managed and direct- 
ed. This latter properly is called the lielm 
or tiller; and sometimes, though improperly, 
the rudder itself. The power of the rudder 
is reducible to that of the lever. As to the 
angle the rudder should make with the keel, 
it is shown, that in the working of ships, in 
order to stay or bear up the soonest pos- 
sible, the tiller of the rudder ought to make 
an angle of 56° with the keel. A narrow 
rudder is best for a ship’s sailing, provided 
she can feel it ; that is, be guided and turn- 
ed by it : for a broad rudder wilt hold much 
water when the helm is put over to any 
side ; but if a ship have a fat quarter, so 
that the water cannot come quick and 
strong to her rudder, she will require a 
broad rudder. The aft-most part of the 
rudder is called the rake of the rudder. 
RUDOLPHINE Tables, a set of astro- 
noraical tables that were published by the 
celebrated Kepler, and so called from the 
Emperor Rudolph, or Rudolphus. 
RUELLIA, in botany, so named in ho- 
nour of Joannes Ruellins, a genus of the 
Didynamia Angiospermia class and order. 
Natural order of Personatae. Acanthi, Jus- 
sieu. Essential character : calyx five-part- 
ed ; corolla subcampanulate ; stamens ap- 
proximating by pairs ; capsule opening by 
elastic teeth. 'There are forty-three species. 
Swartz observes, that the Ruellite are very 
nearly allied to the Justici® in their natural 
order, flowers, fruit, and habit. 
RUIZIA, in botany, so named in honour 
of Don Hipolito Ruiz, a genus of the Mona- 
delphia Polyandria class and order. Natu- 
ral order of Columnifer®. Malvace®, Jus- 
sieu. Essential character: calyx double, 
exterior three-leaved; styles ten; capsule 
ten, one-celled, two-seeded, closely coher- 
ing. There are three species, all natives of 
the Isle of Bourbon. 
RULE, in arithmetic, denotes an opera- 
tion performed with figures, in order to dis- 
cover sums or numbers unknown. The 
fundamental rules are addition, subtraction, 
multiplication, and division. But, besides 
these, there are other rules, denominated 
from their use ; as the rule of Alligation, 
Fellowship, Interest, Practice, Re- 
duction, &c. which see in the alphabetical 
order. 
Rule of Three, Golden Rule, or Rule 
of Proportion, is one of the most essential 
rules of arithmetic; for the foundation of 
which see the article Proportion. It is 
