RAF 
RAJ 
RAJ 
543 
R thc seventeenth letter of our alphabet. 
} In the notes of the antients, R. or RO. 
signifies Roma; R. C. Roinana civitas; 
It. G. C. rei geiendae causa; R. F. E. D. 
recte factum et dictum; R. G. F. regisfilius; 
R. P. res publica, or Romani principes; and 
R.R.R.F.F.F. res Romana ruet ferro, fame, 
flamma. 
Used as a numeral, R antiently-stood for 
eighty, and with a dash over it, thus It, for 
80,000 ; but the Greek r, or signified 100 
In the prescriptions of physicians, R or R. 
stands for recipe, i. e. take. 
RABBETING, in carpentry, the planing 
or cutting of channels or grooves in boards. 
In ship-carpentry, it signifies the letting-in of 
the planks of the ship into the keel ; which, in 
the rake and run of a ship, is hollowed away, 
that the planks may join the closer. 
RABBIT. See Lepus. 
RACHITIS. Sec Medicine. 
RACK. See Arrack. 
RACKOON. See Ursus. 
RADIAL CURVES, are curves of the 
spiral kind, whose ordinates, if they may be 
so called, all terminate in the centre of the 
including circle, appearing like radii of that 
circle, whence the name. 
RADIALIS, or Radijeus. See Ana- 
tomy. 
RADIANT. See Heraldry. 
RADIATED FLOW ERS. See Botany. 
RADIATION, the act of a body emitting 
or diffusing rays of light all round, as from a 
centre. 
RADICLE. See Plants, physiology of, 
Botany, and Germination. 
RADIUS, in geometry, the semidiame- 
ter of a circle, or a right line drawn from the 
centre to the circumference. See Circle, 
and Geometry. 
Radius. See Anatomy. 
RAFF , a sort of float, formed by an as- 
semblage of various planks or pieces of tim- 
ber fastened together side by side, so as to 
be conveyed more commodiously to any 
short distance in a harbour or road than if 
they were separate. The timber and plank 
with which merchant-ships are laden, in the 
different parts of the Baltic Sea, are attached 
together in this manner, in order to float 
them off to the shipping. 
RAFTERS, in building, are pieces of tim- 
ber, which standing by pairs on the raising- 
piece, meet in an angle at the top, and form 
the roof of a building. It is a rule in build- 
ing, that no rafters should stand farther than 
\2 inches from one another: and as to their 
sizes or scantlings, it is provided by act of 
parliament, that principal rafters, from 12 feet 
six inches to 14 feet six inches long, shall be 
five inches broad at the top, and eight at the 
bottom, and six inches thick. Those from 
]4 feet six inches to 18 feet six inches long, 
to be nine inches broad at the foot, seven 
inches at the top, and seven inches thick; 
and those from 18 feet six inches, to 21 feet 
six inches long, to be 10 inches broad at the 
foot, eight at the top, and eight thick. Single 
rafters, eight feet in length, must have four 
inches and a half, and three inches three 
quarters, in their square. Those of nine feet 
long, must be live and four inches square. 
Principal rafters should be nearly as thick 
at the bottom as the beam, and should dimi- 
nish in their length one-fifth or one-sixth of 
their breadth ; the king-posts should be as 
thick as the principal rafters; and their 
breadth according to the size of those that 
are intended to be let into them, the middle 
part being left somewhat broader than the 
thickness. 
RAG WORT. See Senecis. 
ItAGG, rozvlcy, a genus of stones belong- 
ing to the siliceous class. It is of a dusky or 
dark-grey colour, with many small shining 
crystals, having a granular texture, and ac- 
quiring an ochry crust by exposure to the 
air. The specilic gravity is 2.748. It be- 
comes magnetic by being heated in an open 
fire. In a strong lire it melts without addi- 
tion, but with more difficulty than basaltes. 
It was analysed by Dr. Withering, who found 
that 100 parts of it contain 47.5 of siliceous 
earth, 32.5 of argil, and 20 of iron. 
RAJA, ray, a genus of fishes of the class 
amphibia, and of the order nantes. The ge- 
neric character is, mouth situated beneath 
the head, transverse, beset with teeth ; spi- 
racles beneath, five on each side the neck ; 
body in most species sub-rhomboidal. 
This genus, of which there are 19 species, 
is distinguished by the remarkable breadth 
and thinness of the body, the pectoral fins 
appearing like a continuation of the sides 
themselves, being covered with the common 
skin. Their rays are cartilaginous, straight, 
and furnished with numerous swellings or 
knots; the teeth are very numerous, small, 
and placed in ranges over the lips or edges 
of the mouth; the eyes are furnished with 
a nictitating membrane or skin, which can at 
pleasure be drawn over them like an evelid; 
and at some distance above the eyes are situ- 
ated the nostrils, each appearing like a large 
and somewhat semilunar opening edged with 
a reticulated skin, and furnished internally 
with a great many laminated processes di- 
vided by a middle partition ; they are guard- 
ed by an exterior valve : behind the eyes are 
also a pair of holes communicating with the 
mouth and gills : these latter, taken together, 
present a vast extent of surface : the young 
are contained in oblong square capsules, with 
lengthened corners, and are discharged at 
distant intervals, the young animal gradually 
liberating itself from its confinement, and ad- 
hering for some time by the umbilical ves- 
sels. The rays in general feed on the smaller 
kind of crabs, testacea, marine insects, and 
fishes. They are constant inhabitants of the 
sea, lying concealed during part of the wai- 
ter among the mud or sand, from which they 
occasionally emerge and swim to unlimited 
distances. 
1. Raja batis, of a rhomboid shape. The 
skate is one of the largest of the European 
rays, sometimes weighing from one to two 
hundred pounds, and ev< n, according to 
some accounts, not less than three. Its ge- 
neral colour on the upper parts is a pale 
cinereous brown, varied with several darker 
or blackish undulations ; the under part is 
white, marked with numerous, distant, black 
specks; in the male, the pectoral fins are 
beset towards their tips or edges with nume- 
rous small spines; on each side the tail, at 
some distance from the base, is a sharp spine; 
several very strong ones run down the back 
of the tail, and in some specimens a row ot 
smaller ones is visible on each side. As an 
edible fish, the skate is considered as one of 
the best of its tribe, and is an established ar- 
ticle in the European markets, being found 
in great plenty in the adjoining seas, where it 
usually frequents the shores in the manner of 
flat fish. It breeds in the month of March 
and April, and deposits its ova from May to 
September. We are informed by Mr. Wil- 
lughby, that a skate of 200 pounds weight 
was sold in the fish-market at Cambridge to 
the cook of St. John’s college in that univer- 
sity, and was found sufficient to dine the 
whole society, consisting of more than 129 
persons. In October the skate is usually 
poor and thin, begins to improve in Novem- 
ber, and grows gradually better till May, 
when it is considered as in its highest per- 
fection. 
2. Raja clavata, the thornback, grows to a 
very considerable size, though rarely equal 
in magnitude to the skate. In its general 
appearance it resembles that fish, but is some- 
what broader in proportion, and is easily 
distinguished from the skate by the very 
strong curved spines with which its upper 
surface is covered: these- are most conspi- 
cuous down the middle and on each side of 
the back, where four or six, of much larger 
size than the rest, are generally seen ; the 
remaining parts being furnished w ith many 
scattered spines of smaller size, intermixed 
with still more minute ones, and the whole 
skin is of a rough or shagreen-like surface ; 
the back is marked with an uncertain number 
of pale or whitish round spots, of different 
sizes, and which are commonly surrounded 
with a blackish or dark-coloured edge : these 
spots are said to be caused by the shedding 
of the spines at different intervals; along the 
middle of the back runs a single row of strong 
-pines, continued to the tip of the tail ; and it 
often happens that there are three or even 
five rows of spines on this part : the colour 
/ 
