346 Prof. Ch. V. Zenger on a New Steam-gauge. 



same ratio as that in which the pressure increases, which is evi- 

 dently what is required by Mariotte's law in order that an in- 



crease of pressure of one atmosphere may cause the first tube to 

 be filled by the enclosing liquid, and that a further increase of 

 pressure of the same amount may cause the second tube also to 

 be filled, and so on, each equal increment of pressure causing 

 the same rise of the liquid in the manometer-tube. This ad- 

 justment of the capacities is effected as follows : — Let the capacity 

 of a manometer to be divided so as to show pressures up to, say, 

 four atmospheres be called unity, and let v lf % v 3 , and v 4 be the 

 capacities of the first, second, and third tubes, and of the ter- 

 minal globe respectively ; then we have 



