ocr: 2 L E RE P B A, a tripod, with levelling acrews; BB, a vertical pillar, to wlichisattached, C, a mercurial trough, movable by a rack and pinien, aa; DD, a glass - - - - - cylinder, 36 inches long, - - - with an internal diameter of 4 inches, containing three tubes, F,G, H, which communicate with one another and with the exit- pipe, h, by the apparatus 6 Ef E. The rest of the figure will be sufficiently intelligible from the des- eription given in the text. B 3 EL a - J "h A