292 NATURE STUDY REVIEW [9:9— Dec, 1915 



1. The Air. 



The barometer — Gases in the air. 



2 . Capillarity and solvent action of water. 



3. Heat and cold. 



How produced and transferred — wind — keeping heat in or 



out. 

 Freezing and thawing, — Artificial ice. 



4. A study of Machinery. 



The lever, pulleys, cog wheels, belt and belt wheel, in- 

 clined plane, screw, windlass. 



5. Light. 



Sources, speed, reflection, diftusion, refraction, color,, 

 images (camera, etc.). 



6. Sound. 



Vibrations — how sound travels — the speaking tube — the 

 megaphone — speed of sound — echo. 



7. Magnetism. 



8. Electricity. 



The bell — the push button — the telegraph — the electric 

 light — frictional electricity — discussion of other ap- 

 pliances. 



9. Astronomy. 



The solar system — the sun — day and night — differences in 

 temperature in different zones — the planets — the moon 

 — eclipses of sun and moon — the tides — the stars — the 

 constellations. 



A few suggestions regarding the development of certain of the 

 above topics will help to point out a method by which all can be 

 treated. A cardinal principle throughout should be the avoidance 

 of everything technical or abstruse, either in phraseolog\^ or subject 

 matter. Highly scientific generalizations, such for example as the 

 molecular theory or the theory of ether have no i^lace in nature- 

 study. Simple laws and principles such as those governing the 

 operation of machinery ought to be given, but these should be put 

 into concrete form using simple demonstrations. 



In the study of air the first object to achieve may well be to 

 establish in the minds of pupils the reality of this substance which 

 makes so little appeal to the senses. The use of a fan, a pop gun, 

 a bicycle pump, an inverted bottle of water and a wet leather disk 

 for "suction" on a flat surface demonstrates its existence, and a 



