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ter, running forcibly against the side of the pipe, as itappears to do in the figure, is in great part dashed intodrops; the intervals between which being filled by air,this air is successively pushed down by the drops whichfollow, and afterwards escapes as soon as it meets with avent. There seems, however, to be either some inaccu-racy in the description, or some essential part omitted :for in such trials as I have made, when air, thus conveyedinto a perpendicular pipe along with running water, wasdischarged by a lateral aperture, part of the water alwaysaccompanied it in a stream ; and more of the waterseemed to issue out in proportion as the quantity of airintroduced was the greater.

II. A pipe 'with air boles , inserted into an air vessel.

M. Beudor, in his architecture hydraulique, gives amore particular description of a water machine used in .some parts of France : he fays there are four or five forgeson the river Isere, between Roinans and Grenoble, whichhave no other bellows.

The stream is divided into two channels, and each di-vision falls into an upright pipe ten or twelve feet high.Near the tops of the pipes are several holes, made slopingdownwards from the outside to the inside : through theseholes air enters, and is carried down by the water;though the experiments in the following section will shew,that the quantity of air thus introduced is not so great asin the dispositions mentioned hereafter.

The essential difference of this instrument from the fore-going consists in its having an air vessel, or reservoir forthe air, at the bottom. An oval wooden tub, near sevenfeet high, and three or four feet wide, is inverted, and itslower edge let into the ground five or six inches. The4 lower