150 INTRODUCTION TO GENERAL SCIENCE 



cury. The duration of sunshine may then be recorded elec 



trically. 



References : 



1. 1103:104-105. The Anemometer. 



2. 1103 : 123-125. The Psychrometer and the Hair Hygrom- 



eter. 



3. 1103 : 145. The Rain Gauge. 



4. 1103 : 164. The Piche Evaporimeter. 



5. 1304:420-425. Meteorological Instruments. 



6. 1803 : 102-103. The Wet- and Dry-bulb Thermometer. 



7. 1803 : 136-137. Maximum and Minimum Thermometers. 



8. Bulletin No. 235 : 5-8. Weather Bureau. The Sling Psy- 



chrometer and the Dew-point Apparatus. 



9. Bulletin No. 285. Weather Bureau. Measurement of Pre- 



cipitation. 



a. 1101 : 11-41. Weather Instruments. 



b. 1302 : 398-404. Meteorological Instruments. 



110. HOME-MADE WEATHER INSTRUMENTS 



The United States Department of Agriculture in its Year- 

 book for 1907 published directions for constructing home- 

 made weather instruments. Reprints may be obtained, free 

 of charge. 



References : 



Reprint from Yearbook Department of Agriculture. 

 1. 1907. The Weather Bureau and the Public Schools. Pages 

 272-274. Home-made Instruments. 



Pupils should be encouraged to make these simple instru- 

 ments at home and use them. 



111. THE OCEAN 







The ocean occupies about three fourths of the surface of 

 the earth, varying in depth from a few feet to about five 





