THE ANEROID BAROMETER

[A, 376.} until the weight of the erm on nner pre ing upon the liquid in the ve el sustains the column of liquid in the tube. This occurs when the weight of the column of liquid is just equal to that of the column of air of the same diameter resting upon the liquid in the reservoir. This latter weight, which is the atmospheric pre ure, is, therefore, directly proportional to the weight, and hence to the height, of the column in the tube, and the latter is read off from a scale graduated in fractions of an inch, [B.]|—Counterpoised b. Ger., Wageb’. A form of cistern b. invented by S. Borland about the year 1680, in which the barometric tube is suspended from one end of a pivoted beam, a counterpoise being carried by the other end. As the atmospheric re q increases, the mercury in the tube rises, making the tube and its contents heavier, while the sinking of the mercury in the cistern decreases the upward pre ure due to displacement. ConsertE ays the end of the beam to which the tube is attached falls. The variations of pre ure are indicated by the movements of the beam, which may be recorded by a graphic mechanism, so that the instrument may be used as a barograph. [A, 876.]—Differential b. A manom- N N REGNAULT’S BOILING-POINT,