PR o 
the discovery demonstrated. So that a 
problem is to find a tiieor' m. 
Problem, Kepler's, n .istronomy. is the 
determining a planet s place from the time ; 
so cal'ed from Kepler, who first proposed 
it. It was this, to find the position of a 
right line, whicli, passing tbrongli one of 
the foci of an ellipsis, shall cal off an area 
described by its motion, which shaU be in 
any given proportion to the whole area of 
the elhpsis. 
The proposer knew no way of solving the 
problem but by an indirect method ; but 
Sir Isaac Newton, Dr. Keill, &c. have 
since solved it directly and geometrically, 
several ways. 
Problem, Deliacal, or a problem for 
finding two mean proportionals between 
two given lines, in geometry, is the doubling 
of the cube ; it was so called from the 
people of Delos, who, upon consnlting 
the oracle for a remedy against a plague, 
were answered, that the plague should 
cease when Apollo’s altar, which was in 
form of a cube, should be doubled. See 
Cube. 
PROCEDENDO, is a writ which lies 
where a cause is removed out of an inferior 
to a superior court. 
PROCELLARIA, the petrel, in natural 
history, a genus of birds of the order An- 
seres. Generic character; bill strait, but 
hooked at the end j nostrils generally con- 
tained in one tube, at the base of the bill ; 
legs naked a little above the knee ; back 
toe little more than a spur. There are 
twenty-three species, of which Uie following 
are the principal. 
P. gigantea, or the giant petrel, is more 
than three feet long, and about seven wide 
These birds are often seen sailing just above 
the water without moving their wings for 
a long time together, and, being particularly 
alert on the approach of storms, often fill 
the mariner with apprehension and alarm. 
They abound most in southern latitudes, 
and though their principal food is fish, de- 
vour also the putrid carcasses of seals and 
whales. 
P. capensis, or the pintado petrel, abounds 
about the coasts of the Cape of Good Hope. 
These birds are about the size of llie kitti- 
wake gull, and are often oh.served in such 
numbers that many hundreds have been 
taken in one night. They are often taken 
with a rod and line by a hook baited with 
lard. They frequently discharge oil from 
their nostrils on those who hold them, spurt- 
ing it in their faces with great violence. 
PRO 
P. glacialis, or the fulmar petrel, weighs 
nearly a pound and a half, and is found in 
the northern coascs of this island, and thence 
even beyond Iceland and Greenland, where 
the natives use it for food, though its flesh 
is highly offensive to tho.se not used to it. 
The fat is burnt in their lamps. These 
birds subsist chiefly on fish, but often ban- 
quet on the carcases of whales, particularly 
the fat parts, which they afterwards eject 
from their stomachs into the mouths of their 
young. They often spurt it in the faces of 
their enemies and exhibit indeed no other 
mode of resistance. They are stated to 
be so amazingly fat, that, on being passed 
through the hands with great compression, 
the fat flows off like oil. 
P. puflinus, or the shear water petrel, is 
smaller than the last. These birds are found 
in vast numbers in the Orkneys, where they 
are highly valued for their feathers as well 
as flesh. They are, in some places salted 
and barrelled, especially in the Isle of 
Man. In Denmark they sometimes reside 
in rabbit burrows. See Aves, Plate XII. 
fig. 5. 
P. pelagica, or the stormy petrel, is of 
the size of a swallow and rarely seen but at 
sea, sftid in tempestuous weather nurabei-s 
are observed frequently following, as if for 
shelter, in the wakes of vessels. , They dive 
sometimes for half an hour together, and 
live principally upon fish, but will eat a 
variety of offal thrown from ships. In the 
Ferro Islands they arc so astonishingly fat 
that the natives are stated to use them as 
candles after drawing a wick through their 
bodies. See Aves, Plate XII. fig. 6. 
PROCESS, in Iqw, is the manner of pro- 
ceeding in every cause, being the writs and 
precepts that proceed, or go forth upon the 
original upon every action, being either ori- 
ginal or judicial. 
PROCKIA, in botany, a genus of the 
Polyandria Monogynia class and order 
Natural order of Rosaceae, Jussieu. Essen- 
tial character : calyx, three-leaved, besides 
two-leaflets at the base ; corolla none; 
berry five cornered, many seeded. There 
is but one species, viz. P. crucis. 
PROCYON, in astronomy, a-fixed star 
of the second magnitude in the constella- 
tion, called canis minor. 
PRODUCING, in geometry, signifies 
the drawing out a line further, till it have 
any assigned length. 
PRODUCT, in arithmetic and geome- 
try, the factum of two or more numbers, 
or lines, &c. into one another : thus 5X4 
