PERSEUS

, a constellation of the northern hemisphere, being one of the 48 ancient asterisms.

The Greeks fabled that this is Perseus, whom they make the son of Jupiter by Danae. The father of that lady had been told, that he should be killed by his grandchild, and having only Danae to take care of, he locked her up; but Jupiter found his way to her in a shower of gold, and Perseus verisied the oracle. He cut off also the head of the gorgon, and affixed it to his shield; and after many other great exploits he rescued Andromeda, the daughter of Cassiopeia, whom the sea nymphs, in revenge for that lady's boasting of superior beauty, had fastened to a rock to be devoured by a monster. Jupiter his father in honour of the exploit, they say, afterwards took up the hero, and the whole family with him, into the skies.

The number of stars in this constellation, in Ptolomy's catalogue, are 29; in Tycho's 29, in Hevelius's 46, and in the Britannic catalogue 59.

PERSIAN Wheel, in Mechanics, a machine for raising a quantity of water, to serve for various purposes. Such a wheel is represented in plate xx, fig. 1; with which water may be raised by means of a stream AB turning a wheel CDE, according to the order of the letters, with buckets a, a, a, a, &c, hung upon the wheel by strong pins b, b, b, b, &c, fixed in the side of the rim; which must be made as high as the water is intended to be raised above the level of that part of the stream in which the wheel is placed. As the wheel turns, the buckets on the right hand go down into the water, where they are filled, and return up full on the left hand, till they come to the top at K; where they strike against the end n of the fixed trough M, by which they are overset, and so empty the water into the trough; from whence it is to be conveyed in pipes to any place it is intended for: and as each bucket gets over the trough, it falls into a perpendicular position again, and so goes down empty till it comes to the water at A, where it is filled as before. On each bucket is a spring r, which going over the top or crown of the bar m (fixed to the trough M) raises the bottom of the bucket above the level of its mouth, and so causes it to empty all its water into the trough.

Sometimes this wheel is made to raise water no higher than its axis; and then instead of buckets hung upon it, its spokes C, d, e, f, g, h, are made of a bent form, and hollow within; these hollows opening into the holes C, D, E, F, in the outside of the wheel, and also into those at O in the box N upon the axis. So that, as the holes C, D, &c, dip into the water, it runs into them; and as the wheel turns, the water rises in the hollow spokes, c, d, &c, and runs out in a stream P from the holes at O, and falls into the trough Q, from whence it is conveyed by pipes.

Persian

, or Persic, in Architecture, a name common to all statues of men; serving instead of columns to support entablatures.

Persian Era and Year. See Epoch and Year.

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Entry taken from A Mathematical and Philosophical Dictionary, by Charles Hutton, 1796.

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PERISTYLE
PERITROCHIUM
PERPENDICULAR
PERPETUITY
PERRY (Captain John)
* PERSEUS
PERSPECTIVE
PERTICA
PETARD
PETIT (Peter)
PETTY (Sir William)