DIA 
DIA 
sential character : calyx tme-leafed ; cap- 
sule three-celled ; filaments three-cusped. 
There is but one species, viz. D. scabra, a 
tree about the height of a man, and very 
much branched. It is a native of Japan, 
where the leaves are used by joiners in 
smoothing and polishing. 
DEW, a dense moist vapour, falling on 
the earth in the form of a misling rain, 
while the sun is below the horizon. See 
Meteorology ; Vapours, ascent of. 
Dew worm. See Lumbricds. 
DEWLAP, the membranous fleshy sub- 
stance that hangs down from the throats of 
neat cattle. 
DEXTANS, in Roman antiquity, ten 
ounces or of their as. See As. 
DEXTER, in heraldry, an appellation 
given to whatever belongs to the right side 
of a shield, or coat of arms : thus we say, 
bend dexter, dexter point, &c. 
DEXTROCHERE, or Dbstrochere, 
in heraldry, is applied to the right arm 
, painted in a shield, sometimes naked, some- 
times clothed, or adorned with a bracelet ; 
and sometimes armed, or holding some 
moveable, or member used in tire arms. 
DIABETES, an excessive discharge of 
urine, which comes away crude, and ex- 
ceeds the quantity of liquids drank. See 
Medicine. 
DIACAUSTIC carve, a species of caus- 
tic curves formed by refraction. Thus if 
we imagine an infinite number of rays B A, 
BM, BD, &c. (Plate Miscel. Fig. 6.) issuing 
from the same luminous point B to be re- 
fracted to or from tile perpendicular M C, 
by the given curve AMD, and so, that 
CE, the sines of the angles of incidence 
C M E, be always to C G, the sines of the 
refracted angles C M G, in a given ratio, 
then the curve HFN, wliich touches all the 
refracted rays, is called the diacaustic, or 
caustic by refraction. 
DIACHYLON, a well known plaster, 
composed of a solution of litharge in olive 
oil: it is called emplastruni lithargyri. See 
Pharmacy. 
DIADELPHIA, in botany, two brother- 
hoods; the seventeenth class in Linnaeus’s 
sexual system, consisting of plants whose 
flowers are hermaphrodite, and have the 
stamina, or male organs, united below into 
two sets of cylindrical filaments. See Pa- 
PILIONACE.®. 
The orders in this class are founded on 
the number of stamina, considered as dis- 
tinct. Some pea-bloom, or buttei-fly-shaped 
flowers, have five stamina, or male organs, 
as monnieria ; some six, as fumatory ; some 
eight, as milk-wort ; some ten, as broom, 
bladder-sena, lupine, lady’s-finger, vetch, 
and the far greater number of butterfly- 
shaped flowers. It is only the last order 
that is included in the natural lainily papili- 
ouaceae ; the remaining four genera are dis- 
tributed among other families, to which 
they have, at least, an equal alliance. The 
names given by former botanists to the ex- 
tensive class of plants in question, are much 
riiore characteristic of their nature and ap- 
pearance, than that of diadelphia. The 
figure of the flowers and fruit never varies : 
the latter being alivays of the pod-kind ; the 
former of the butterfly shape. On the 
other hand, the two sets of united stamina, 
the only classic character expressed in the 
Linnaean title, are never to be traced 
without difficulty ; for one of the sets only 
is properly united ; the other consisting of 
a single filament, which, in most plants, ad- 
heres so closely to its kindred set, that it 
cannot be separated without the application 
of a pin or needle for that purpose. In 
some even, no separation can be effected 
by this means. 
DIADEM, in heraldry, is applied to 
certain circles, or rims serving to inclose the 
crowns of sovereign princes, and to bear 
the globe and cross, or the flower de luces 
for their crest. The crowns of sovereigns are 
bound, some with a greater, and some with 
a less number of diadems. The bandage 
about the heads of moors on shields is also 
called diadem, in blazoning. 
DliERESIS, in grammar, the division of 
one syllable into two, which is usually noted 
by two points over a letter, as aulai, instead 
of aulae, dissoliienda for dissolvenda. 
DIAGNOSTIC, in medicine, a tem 
given to those signs which indicate the 
present state of a disease, its nature and 
cause. 
DIAGONAL, in geometry, a right line 
drawn across a quadrilateral figure, from one 
angle to an other, by some called the dia- 
meter, and by others the diameter of the 
figure. Thus A C, (Plate IV. Miscel. fig. 7.) 
is called a diagonal. 
It is demonstrable, 1. That every diago- 
nal divides a parallelogram into two equal 
parts. 2. That two diagonals drawn in any 
parallelogram bisect each other. 3. A line 
F G, passing through the middle point of 
the diagonal of a parellelogram, divides tire 
figure into two equal parts. 4. The diago- 
nal of a square is incommensurable with 
one of its sides. 3. That tire, sum of the 
squares of the two diagonals of every parel- 
lelogram is equal to the sum of the squares 
