THE OCEAN OF AIR 



commercial aneroid barometer and a view of its work- 

 ing parts are pictured in Figures 4 and 5. Can you find 

 the wavy box, the levers, and the springs? 



What are some of the uses of barometers? They 

 find their greatest use in predicting changes in the 

 weather, for it has been found that when the pres- 

 sure of the air is low we usually have stormy or bad 

 weather, while high pressure usually means fair or 



no. 11 



clear weather. Mercury barometers are generally used 

 where they do not have to be disturbed, as for ex- 

 ample, in laboratories, while aneroids, being more 

 easily carried, are used in the office, house, or where- 

 ever barometer readings are needed. Aneroid barom- 

 eters are made in many sizes ranging from the pocket 

 size, used by mountain climbers, up to five or six 

 inches in diameter, used by surveyors and map mak- 

 ers to find the height of a certain point above sea 

 level. When used for these latter purposes the aneroid 

 must be very accurate ; in fact, some are made so 

 extremely sensitive that they will show a difference 

 in pressure of one thousandth of an inch of mercury 

 column. 



The rapid development of airplanes and dirigibles 

 has greatly increased the use of aneroid barometers, 

 which aviators always include in their equipment. 

 When used in this way the instruments are called 

 altimeters. The scale is made to read in feet of eleva- 



AS. ; 



x. ...: 

 ' i ' '' 



v 



1 1 1 ; -, -. ' 



tion above the earth's surface, making it possible for 

 the pilot to tell his elevation by reading the aneroid 

 on the instrument panel. The picture of an altimeter 

 used in aviation is shown in Figure 12. 



When records of altitude are sought by aviators or 

 balloonists, a recording aneroid barometer called a 

 barograph is used. This instrument works on the same 

 principle as the ordinary aneroid except that the mo- 

 tion of the little box operates a pen which traces a 

 line in ink on a paper scale. The scale is fastened to a 

 revolving drum which is turned by clockwork. 



Barographs are used by weather bureaus and some 



Courtesy Taylor Instrument Company 



FIG. 13. RECORDING BAROGRAPH 



industries where the daily pressure readings are taken 

 and filed away for any future reference. Figure 13 

 shows a recording barograph. 



REFERENCES FOR FURTHER STUDY 



Texts 



Taylor Instrument Company 



FIG. 12. ALTIMETER 



Caldwell and Curtis, Science for Today, pp. 17-26 



Clement, Collister, and Thurston, Our Surroundings, pp. 37- 



40 

 Hunter and Whitman, My Own Science Problems, pp. 43-47 



and 52-58; Science in Our World of Progress, pp. 70-72; 



Science in Our Social Life 

 Lake, Harley, and Welton, Exploring the World of Science, 



pp. 10-19 

 Pieper and Beauchamp, Everyday Problems in Science, pp. 



112-119 

 Powers, Neuner, and Bruner, The World Around Us, Chaps. 



8, 9, 10; This Changing World, pp. 165-171 

 Skilling, Tours through the World of Science, pp. 75-81 

 Van Buskirk and Smith, The Science of Everyday Life, pp. 



7-18 

 Watkins and Bedell, General Science for Today, pp. 1-10 and 



19-24 



Webb and Beauchamp, Science by Observation and Experi- 

 ment, pp. 223-227 and 233-235 

 Wood and Carpenter, Our Environment: Its Relation to Us, 



pp. 139-148; Our Environment: How We Use and Control 



It, pp. 94-108 



Special References 



Jameson, The Barometer as the Foot-rule of the Air 

 Burns, The Story of Great Inventions 



