ROE 
fn being funnel-shaped, that is having a tube, and a border 
spreading out; whereas in campanula, the corolla is bell- 
shaped, or spreads gradually from the bottom.—When a 
flower is recently expanded, five shades of colour appear, 
which being disposed in circles, produce a striking effect: 
fhe bottom of the flower is white, of a yellowish cast, next 
Succeeds a circle of deep blue inclining to black, with ^sur¬ 
face highly glazed, the next circle is greyish-blue resembling 
satin, the next nearly white, and the outermost pale purple. 
The anthers at first are closely applied to the surface of the 
corolla, and resemble so many small ridges; the stigma, as 
in many other flowers, does not assume its true appearance 
till the corolla is on the decay ; then it becomes bifid. Cap¬ 
sule ovate-cylindrical. 
2. Roella squarrosa, or trailing roella. — Leaves ovate 
toothed ciliate, flowers terminating aggregate. 
3. Roella decurrens, or decurrent roella. —Leaves lanceo¬ 
late ciliate, quite entire, decurrent, flowers solitary termina¬ 
ting. 
4. Roella muscosa, or mossy roella.—Herbaceous, diffused, 
leaves ovate toothed reflex, flowers terminating solitary. 
' 5. Roella spicata, or spiked roella. —• Leaves lanceolate 
ciliate, flowers terminating aggregate.—All these plants are 
natives of the Cape of Good Hope. 
Propagation and Culture. —The first and other shrubby 
s'pecies may be increased by cuttings, but not very readily. 
They are not so easy of culture as many others. They must 
be kept in a dry stove, good green-house, or glass case. 
Roella reticulata is Gorteria ciliaris. 
’ ROEMER (Olaus), a celebrated Danish astronomer and 
mathematician, who flourished in the 17th and early part of 
the 18th century, was the son of a respectable merchant at 
Arhusen, in Jutland, where he was bom in the year 1644. 
From an elementary school at his native city, he was trans¬ 
planted to the University of Copenhagen, in the year 1662, 
and soon distinguished himself by the progress which he 
made in his academical studies, and particularly in the 
mathematical sciences, which were the favourite subjects of 
his pursuit. By assiduous application he had become so 
expert in those sciences, and such an able astronomer, that 
in the year 1671, having been introduced to M. Picard, of 
the Academy of Sciences at Paris, who was sent by Lewis 
XIV., to make astronomical observations in the northern 
regions, that gentleman was so greatly surprized and pleased 
With him, that he engaged him to accompany him when he 
returned to France. Here he presented him to the King, who 
appointed him mathematical preceptor to the Dauphin, and 
Settled a pension upon him. Roemer was united with 
Picard and Casina, in making astronomical observations; 
and in 1672, he was admitted a member of the Royal 
Academy of Sciences at Paris. In this city he resided ten 
years, during which he acquired a high reputation by his dis¬ 
coveries ; and he is even said to have complained afterwards, 
that his coadjutors took the honour of many things which 
properly belonged to him. Here it was that he, for the first 
time, found out the velocity with which light moves, by 
means of the eclipses of Jupiter’s satellites. For many years 
he had observed that, when Jupiter was at the greatest 
distance from the earth, at which he could be observed, the 
emersions of his first satellite happened constantly fifteen or 
sixteen minutes later than the calculations gave them. Hence 
he concluded, that the light reflected by Jupiter was thus 
long in passing through the excess of distance, and, conse¬ 
quently, that it took up sixteen or eighteen minutes in 
running over the diameter of the earth’s orbit, and eight or 
fline in coming to us, provided that its velocity was nearly 
uniform. This discovery met at first with much opposition; 
but it was afterwards confirmed by Dr. Bradley. In the 
year 1681, Roemer was recalled to his own country by 
Christian V., King of Denmark, who appointed him pro¬ 
fessor of astronomy at the University of Copenhagen, and 
gave' him the title of his own mathematician, with a con¬ 
siderable salary. His Majesty also employed him in reform¬ 
ing the coin, improving the public buildings, regulating the 
weights and measures, and in surveying and laying out the 
« Vol; XXII. No. 1493. 
R 0 G 1$5 
high roads throughout the kingdom : offices which he dis¬ 
charged with the greatest credit and satisfaction. In 1687, 
the King directed him to travel through Germany, France, 
England, and Holland, in order to collect such information 
on a variety of points, as might be applied to beneficial pur¬ 
poses in Denmark. Upon his return home during the fol¬ 
lowing year, he was made counsellor of the chancellery; 
and in 1693, assessor of the supreme tribunal of justice. 
After the death of Christian V., Roemer was distinguished 
by the favour of his successor, Frederic IV., who, in 1705, 
appointed him burgomaster of Copenhagen, and in 1706, 
honoured him with the dignity of counsellor of state. This 
able man was preparing to publish the result of his observa¬ 
tions, when he died in 1710, a few days before he had com¬ 
pleted the 66th year of his age. In 1753, Peter Horrebow, 
who had been his disciple, and was then professor of astro¬ 
nomy at Copenhagen, published, in a 4to. volume, various 
observations of Roemer, with his method of observing, under 
the title of “ Basis Astronomise.” In the different volumes 
of the “ Memoires” of the Royal Academy of Sciences at 
Paris, of the institution of 1666, may also be seen various 
accounts of his astronomical observations, and other pieces 
communicated by him, particularly in Vols. I. and X. of 
that collection .—Albarti Thurce Idee Hist. Lit. Dan. 
Hutton's Math. Diet. 
ROENENG, a long measure in Siam, equal to one league, 
containing 4204 English yards, or 2§ miles nearly. 
ROER, or Ruhr, the name of two rivers in' the west of 
the Prussian states. The one flowing through the provinces 
of the Lower Rhine, and Cleves and Berg, passes by Duren 
and Juliers, and falls into the Maese. The other rises near 
Winterburg, in Westphalia, flows-westward, till it joins the 
Rhine between Ruhrort and Duisburg. It is rendered 
navigable by means of sluices, but is rapid, and frequently 
does considerable injury by overflowing its banks. 
ROERORT, or Ruhrort, a town of the Prussian states, 
in the duchy of Cleves, at the confluence of the Roer and 
the Rhine. Population nearly 1000; 1'5 miles north of 
Dusseldorf. 
ROEULX, a town of the Netherlands, in the province of 
Hainault, situated in a pleasant district. Population 2500 ; 
8 miles east-north-east of Mons. 
ROFFIGNAC, a village in the west of France, depart¬ 
ment of the Lower Charente, with above 1000 inhabitants. 
ROFRANO, a town of Naples, in the Principato Citra. 
Population 2000; 12 miles north-north-west of Policastro.- 
ROG, two small islands in the gulf of Finland, on the 
coast of Esthonia, inhabited by Swedes, but belonging to 
Russia. 
ROGA, ooya, a donative, or present, which the Augusti, or 
emperors, made to the senators, magistrates, and even the 
people; and the popes, or patriarchs, to their clergy. 
The emperors used to distribute these rogae on the first day 
of the year, or on their birth-day, or on the natalis dies of the 
cities: the popes and patriarchs in Passion Week. 
This custom of - rogae, or largesses, was introduced by the 
tribunes of the people, to gain the populace more effectually 
over to their interest. The emperors at length took it up, 
and made such distributions to the people, and even to the 
soldiery, who are hence called by the Greek writers of the 
middle age goyalooet;. 
ROGA, was also used for the 'ordinary pay of the 
soldiery. 
ROGARSTONE, a hamlet of England, in Monmouth¬ 
shire ; 20 miles west of Newport. Population 650. 
ROG ART, a parish of Scotland, in the county of 
Sutherland, of an irregular square form, about 10 miles in 
extent in every direction. Population 2148. 
ROGASEN, a town of Prussian Poland, in the govern¬ 
ment of Posen, on a lake. Of its population, 3500, nearly a 
third are Jews.' The chief employment is the weaving and 
sale of woollens; 24 miles north-byreast of Posen. 
ROGATE, a parish of England, in Sussex; 7 miles west- 
by-north of Midhurst. Population 595. 
ROGATIO, in the Roman Jurisprudence, a demaud made 
3 B by 
