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 ANEROID BAROMETER 



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 



