Page images
PDF
EPUB
[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][ocr errors][merged small][merged small][merged small][ocr errors][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][ocr errors][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][ocr errors][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][ocr errors][ocr errors][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][ocr errors][ocr errors][ocr errors][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][graphic][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small]
[merged small][subsumed][merged small][merged small][subsumed][subsumed][subsumed][merged small][merged small][subsumed][subsumed][merged small][merged small][merged small][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][merged small][merged small][merged small][ocr errors][merged small][graphic][ocr errors][subsumed][subsumed][subsumed][subsumed][subsumed][ocr errors]

Pneumatic may offer of making them highly useful. A gentleman's Engines. house in the country may thus be supplied with water by a machine that will cost little, and hardly go out of repair. The last pneumatical engine which we shall speak of at present is the common fanners, used for winnowing grain, and for drawing air out of a room and we have but few observations to make on them.

The wings of the fanners are inclosed in a cylinder or drum, whose circular sides have a large opening BDE Fig.202. (fig. 102.) round the centre, to admit the air. By turning the wings rapidly round, the air is hurried round along with them, and thus acquires a centrifugal tendency, by which it presses strongly on the outer rim of the drum: this is gradually detached from the circle as at KI, and terminated in a trunk IHGF, which goes off in a tangential direction; the air therefore is driven along this passage.

If the wings were disposed in planes passing through the axis C, the compression of the air by the anterior surface would give it some tendency to escape in every direction, and would obstruct in some degree the arrival

of more air through the side-holes. They are therefore Pneumatic reclined a little backward, as represented in the figure. Engines. It may be shown that their best form would be that of a hyperbolic spiral a bc; but the straight form approaches sufficiently near to the most perfect shape.

Much labour is lost, however, in carrying the air round those parts of the drum where it cannot escape. The fanners would either draw or discharge almost twice as much air if an opening were made all round one side. This could be gradually contracted (where required for winnowing) by a surrounding cone, and thus directed against the falling grain: this has been verified by actual trial. When used for drawing air out of a room for ventilation, it would be much better to remove the outer side of the drum entirely, and let the air fly freely off on all sides; but the flat sides are necessary, in order to prevent the air from arriving at the fanners any other way but through the central holes, to which trunks should be fitted leading to the apartment which is to be ventilated. See BAROMETER and. BAROMETRICAL MEASUREMENTS, SUPPLEMENT.

Pneumatosis

Pococke.

РОС

PNEUMATOSIS. See MEDICINE, N° 336. PNEUMONIA. See MEDICINE, N° 183. PNEUMONICS, in Pharmacy, medicines proper in diseases of the lungs, in which respiration is affected. PO, a large and celebrated river of Italy, which has its source at Mount Viss in Piedmont, and on the confines of Dauphiny. It runs through Piedmont, Montferrat, the Milanese, and duchy of Mantua; from thence it runs to the borders of the Parmesan, and a part of the Modenese ; and having entered the Ferrarese, it begins to divide at Ficheruolo, and proceeds to discharge itself into the gulf of Venice by four principal mouths. As it passes along, it receives several rivers, and often overflows its banks, doing a great deal of mischief: the reason of which is, that most of those rivers descend from the Alps, and are increased by the melting of the

snow.

POA, MEADOW-GRASS; a genus of plants belonging to the pentandria class, and in the natural method ranking under the fourth order, Gramina. See BOTANY and AGRICULTURE Index.

POCHETTI. See BARBATELLI. POCOCKE, DR EDWARD, a learned oriental scholar, was the eldst son of the Rev. Edward Pococke; and was born at Oxford in 1604, where he was also educated. In 1628 he was admitted probationer-fellow of his college, and about the same time had prepared an edition of the Second Epistle of St Peter, the Second and Third of St John, and that of St Jude, in Syriac and Greek, with a Latin Translation and Notes. In 1629 he was ordained priest, and appointed chaplain to the English merchants at Aleppo, where he continued five or six years; in which time he distinguished himself by his fortitude and zeal while the plague raged there.. At length returning to England, he was in 1636 appointed reader of the Arabic lectures founded by Archbishop Laud. Three years after he went to Constanti

[merged small][ocr errors]

nople, where he prosecuted his studies of the eastern Pococke. tongues, and procured many valuable manuscripts. Af ter near four years stay in that city, he embarked in 1640; and taking Paris in his way, visited Gabriel Sionita the famous Maronite, and Hugo Grotius. In 1643 he was presented to the rectory of Childrey in Berks; and about three years after married the daughter of Thomas Burdett, Esq. About the middle of 1647 he obtained the restitution of the salary of his Arabic lecture, which had been detained from him about three years. In 1648 King Charles I. who was then prisoner in the isle of Wight, nominated Mr Pococke to the professorship of Hebrew, and the canonry of Christ-church annexed to it; but in 1650 he was ejected from his canonry for refusing to take the engagement, and soon after a vote passed for depriving him of his Hebrew and Arabic lectures; but several governors of houses, &c. presenting a petition in his favour, he was suffered to enjoy both these places. He had some years before. published his Specimen Historia Arabum ; and now appeared his Porta Mosis: and soon after the English Po- · lyglot edition of the Bible, to which he had largely contributed, and also Eutychius's Annals, with a Latin version. At the Restoration, he was restored to the canonry of Christ-church, and also received the degree of doctor of divinity. He then published his Arabic version of Grotius's Treatise of the Truth of the Christian Religion; and an Arabic poem entitled Laimato l' Ajam, with a Latin translation and notes. Soon after he published Gregory Abul Pharajius's Historia Dynastiarum. In 1674 he published an Arabic version of the chief parts of the Liturgy of the church of England ; and a few years after his Commentary on the Prophecies of Micah, Malachi, Hosea, and Joel. This great man died in 1691, after having been for many years confessedly the first person in Europe for eastern learning, and was no less worthy of admiration for his uncommon

modesty

« ՆախորդըՇարունակել »