DESCRIPTION

OF

THE FJLATES.

PLATE I.*

A Perspective view of an improved Gazometer. Tt consists ofa cylindrical vessel, made of japanned copper, or iron, a. and aglass cylindrical vessel, b. The japanned vessel is furnished withtwo stop-cocks, one of which is fixed at the top, and the other atthe bottom, on opposite sides of the vessel. From the uppercock, a tube, cc. runs down the outside of the vessel, a. andunder its bottom, to the cock, l. At the centre of the vesselthis tube branches upwards through the bottom of the vessel, a.and thus a communication is made with the stop-cocks and theglass vessel, b. which is suspended in the vessel, a. by means ofweights and pulleys contained in the bent tube, a a. A gradu-ated rod, affixed, by means of a cap, to the vessel, b. expresses,by the coincidence of any of its divisions with the aperture, x. thecapacity of the emerged part of the glass vessel, and thereforemeasures the quantity of gas contained in it. In using this ap-paratus, the vessel a. is filled with water, up to the apperture of

Z

Facing the title-page of vol. i.