Levels and level bubbles

Section I of the paper gives the results of measurement of density, surface tension and viscosity of several liquids for use in levels; the liquids are benzol, xylol, chloroform, alcohol and ether. Section II deals with the corresponding measurements on petroleum ethers distilled at various ranges of temperature, the ether distilled at 40°-50° C. being largely used for levels. Section III gives measurements connecting temperature and length of bubble, with tubes of the ordinary cylindrical type, Section IV the relation between the damping of the movement of the bubble and its length, and Section V the relation between damping and diameter of tube. Section VI deals with the calibration of levels, with particular relation to the presence of faults in the tube. The determination of the longitudinal radius of curvature of the tube is made, as well as the effect of departures from the circular form upon the calibration curve of the level. Section VII describes a new method of obtaining calibration curves, by photographing the image of the bubble in a plane mirror, so that the position of the bubble upon the scale is obtained for successive tilts given to the tube. In Section VIII the relations between temperature and width and depth of bubble are obtained, and the results applied to an explanation of the bubble of Messrs E. R. Watts and Son, Ltd., which has the same length at all temperatures.