THE ANEROID BAROMETER 
103 
any two flags or fixed points, through the corresponding 
points on paper, to an intersection which will fix the 
point occupied. 
7. Fill in the shore line as the other work progresses, 
whatever at the time is nearest the instrument, by traverses, 
sketching, etc. 
SECTION VI 
THE ANEROID BAROMETER 
The aneroid barometer is a cheap and handy instrument 
which, when carried from one point to another, will tell 
approximately their difference in height. This it does by 
measuring the pressure of the air, varying as that does 
when one goes up or 
down hill. 
The essential parts 
of an aneroid bar¬ 
ometer are out of 
sight. The instru¬ 
ment consists of a 
vacuum box with one 
very flexible and sen¬ 
sitive side, which 
works in and out 
with varying pres¬ 
sure of the air. This 
slight movement is 
multiplied, and con¬ 
verted into the cir¬ 
cular motion of the 
pointing hand seen 
on the face of the 
instrument. At sea 
level the hand points 
to one part of the 
dial. As the instru¬ 
ment is carried up a hill or mountain the hand, worked by 
expansion of the box within, turns round to the left. The 
Aneroid Barometer 
