Legal 
in the cylinder of the barometer one inch, it will rife in the tube 
of the refervoir one inch from to O; therefore, as there will be 
a greater quantity of mercury in the tube of the refervoir, the 
barometer will not remain in its firft pofition, but will float 
higher by one inch, that is, fuppofing the cylinder of the baro- 
meter and the tube of the refervoir to contain equal quantities in 
equal diftances; but as that part of the barometer which was 
above the furface of the mercury in the tube of the refervoir 
when the mercury was at 29:, is become lighter in proportion as 
the mercury left the cylinder, fo will there be a portion of the 
tube of the barometer from under the furface of the mercury in 
the tube of the refervoir, and confequently the barometer will 
float higher than one inch in proportion to its decreafe of weight, 
and the x will be above the furface 0, fo that the vernier will 
have moved more than one inch; therefore the divifions on the 
feale B C will be increafed. [When the mercury afcends the 
contrary will take place.] But as the paper moved horizontally 
* during the time that the mercury defcended in the cylinder, 
and as the pencil D marked the paper, the exaét height of the 
mercury will be traced on the paper at every hour and minute. 
N. B. Tue divifions may be enlarged on the fcale BC by en- 
creafing the diameter of the cylinder of the barometer and 
lenthening the tube of the refervoir and the refervoir. 
