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Pneumatic may offer of making thein highly useful. A gentleman's of more air through the side-boles. They are therefore Pneumatic
machine that will cost little, and hardly go out of repair. It may be shown that their best form would be that of a
The last pneumatical engine which we shall speak of hyperbolic spiral abc; but the straight form approaches
round those parts of the drum where it cannot escape.
or drum, whose circular sides have a large opening BDE twice as much air if an opening were made all round Fig. 202. (fig. 102.) round the centre, to admit the air. By one side. This could be gradually contracted (where
turning the wings rapidly round, the air is hurried required for winnowing) by a surrounding cone, and
goes remove the outer side of the drum entirely, and let the
cessary, in order to prevent the air from arriving at the If the wings were disposed in planes passing through fanners any other way but through the central boles, the axis C, the compression of the air by the anterior to which trunks should be fitted leading to the apartsurface would give it some tendency to escape in every ment wbich is to be ventilated. See BAROMETER and. direction, and would obstruct in some degree the arrival BAROMETRICAL MEASUREMENTS, SUPPLEMENT.
PNEUMATOSIS. See MEDICINE, N° 336. nople, where he prosecuted his studies of the eastern Pococke. tosis PNEUMONIA. See MEDICINE, No 183. tongues, and procured many valuable manuscripts. Af Pococke.
PNEUMONICS, in Pharmacy, medicines proper in ter near four years stay in that city, he embarked in diseases of the lungs, in which respiration is affected. 1640; and taking Paris in his way, visited Gabriel Sio
PO, a large and celebrated river of Italy, which has nita the famous Alaronite, and Hugo Grotius. In 1643 its source at Mount Viss in Piedmont, and on the con- he was presented to the rectory of Childrey in Berks ; fines of Dauphiny. It runs through Piedmont, Mont- and about three years after married the daughter of ferrat, the Milanese, and duchy of Mantua; from thence Thomas Burdett, Esq. About the middle of 1647 he it runs to the borders of the Parmesan, and a part of obtained the restitution of the salary of his Arabic lecthe Modenese ; and having entered the Ferrarese, it be- ture, which had been detained from him about three gins to divide at Ficheruolo, and proceeds to discharge years. In 1648 King Charles I. who was then prisoner itself into the gulf of Venice by four principal mouths. in the isle of Wight, nominated Mr Pococke to the proAs it passes along, it receives several rivers, and often fessorship of Hebrew, and the canonry of Christ church overflows its banks, doing a great deal of mischief: the annexed to it; but in 1650 he was ejected from his careason of which is, that most of those rivers descend nonry for refusing to take the engagement, and soon from the Alps, and are increased by the melting of the after a vote passed for depriving him of his Hebrew and
Arabic lectures ; but several governors of houses, &c. POA, MEADOW-GRASS; a genus of plants belonging presenting a petition in his favour, he was suffered to to the pentandria class, and in the natural method rank- enjoy both these places. He had some years before · ing under the fourth order, Gramina. See BOTANY published his Specimen Historiæ Arabum ; and now apand AGRICULTURE Inder.
peared bis Porta Mosis : and soon after the English Po- .
lyglot edition of the Bible, to which he had largely