KOT 
the same time continues to deposit this sub- 
stance, a relapse may be dreaded. It ap- 
|)ears in the form of red flakes, and adheres 
strongly to the sides of the vessel. If the 
urine be heated, this sediment is again dis- 
solved. This substance was formerly con- 
sidered by chemists as the uric acid. If into 
fresh urine, a little nitric acid is dropped, it 
becomes muddy, and a precipitate is form- 
ed, The nitric acid, and the substance to 
which the name of rosacic acid has been 
given, combine togetiier, and are deposited. 
The uric acid, being much less soluble than 
•the rosacic acid, it is very easy to separate 
•thdm. All that is necessary is, to pour boil- 
ing water on the sediments, and to wash 
them on the same filter, in which case, the 
uric acid remains behind. 
ROSMARINUS, in botany, a genus of 
the Diandria Monogynia class and order, 
iiatural order of Verticillatae. Labiat®, 
Jussieu. Essential character : corolla un- 
equal , with the upper-lip two-parted ; fila- 
ments long, curved, simple, with a tooth. 
There are two species, viz. R. officinalis, 
officinal rosemary ; and R. cliilensis, Ghili 
rosemary. 
ROTACEjE, in botany, the name of the 
twentieth order in Linnmus’s Fragments of 
a Natural Method, consisting of plants with 
one flat, wheel-shaped petal. Among the 
genera of this order is the gentiana, the root 
of which is a well-known stomachic, and 
makes a principal ingredient in bitters. 
The plant grows plentifully in the moun- 
tainous parts of Germany, from whence the 
roots are brought to England for medicinal 
purposes. The cistus, or rock-rose, and the 
hypincum, or St. John’s wort, have been 
annexed also to this order. It may be ob- 
served, that gum labdanum is an odorife- 
rous balsam, or resin, which is found on a 
species of the rock-rose, viz. the cistus la- 
danifera, that grows naturally in the Le- 
vant. This substance is collected by the 
natives by means of leathern thongs, rub- 
bed gently over the surface of the shrub 
which produces it. From a species of the 
hypericum, an oil is extracted, that proves 
an excellent vulnerary. 
ROTALA, in botany, a genus of the Tri- 
andria Monogynia class and order. Natu- 
ral order of Caryophylle®. Essential cha- 
racter : calyx three-toothed ; corolla none ; 
capsule three-celled, many seeded. There 
is but one species, viz. R. verticillaris, a na- 
tive of the East Indies. 
ROT-ATION, in geometry, a term chief- 
ly applied to the circumvolution of any sur- 
ROU 
face round a fixed and immoveable line, 
which is called the axis of its rotation : and 
by such rotations it is, that solids are con- 
ceived to be generated. The late ingenious 
M. de Moivre shows how solids, thus gene- 
rated, may be measured or cubed. His 
method is this : for the fluxion of such so- 
lids, take the product of the fluxion of the 
absciss, multiplied by the circular base ; 
and, suppose the ratio of a square to the cir- 
cle inscribed in it to be 2 ; then the equa- 
tion expressing the nature of any circle, 
whose diameter is d, k yy zzzd x — xx. 
’therefore - ^ ^ — 2-^ is the fluxion of a 
n 
portion of the sphere ; and, consequently, 
the portion itself 4i d r r — x- r x’, and the 
circumscribed cylinder is - ^ ■ and 
n 
therefore the portion of the sphere is to the 
portion of the circumscribed cylinder, as 
id-— ixtod — X. 
ROTHIA, in botany, so named in ho- 
nour of Albrecht Wilhelm Roth, physician 
at Bremen ; a genus of the Syngenesia Po- 
lygamia ^qualis class and order. Natural 
order of Composit® Semiflosculos®. Cichc- 
race®, Jussieu. Essential character : calyx 
many-leaved, in a single row, equal, woolly ; 
receptacle in the ray chaffy, in the disk vil- 
lose ; seeds in the ray bald, in the disk pap- 
pose. There is only one species, viz. R. an- 
dryaloides. 
ROTTBOELLIA, in botany, so named 
in memory of Christian Friis Rottboel, Pro- 
fessor of Botany, at Copenhagen ; a genus 
of the Polygamia Monoecia class and order. 
Natural order of Gramma, Gramine®, or 
Grasses. Essential character : rachis joint- 
ed, roundish, in most species filiform ; ca- 
lyx ovate, lanceolate, flat, one or two-valv- 
ed ; florets alternate on a flexuose rachis. 
There are seventeen species. 
ROUND, in a military sense, signifies a 
walk which some officer, attended with a 
party of soldiers, takes in a fortified place 
around the ramparts, in the night-time, in 
order to see that the centries are watchful, 
and every thing in good order. The cen- 
tries are to challenge the rounds at a dis- 
tance, and rest their arms as they pass, to 
let none come near them ; and when the 
round comes near the guard, the centry 
calls aloud, “ Who comes there ?” and be- 
ing answered, “ the rounds he says 
“ stand apd then calls the corporal of the 
guard, who draws his sword, and calls also, 
“ Who comes there and when he is an- 
