24 TEACHING SCIENCE IN THE ELEMENTARY SCHOOL

than warm air," and with Number 3, 4, 5, from the upper grades,
"Wind is due to unequal atmospheric pressures," "Factors, such
as altitude and moisture, contribute to'atmospheric pressure",
"A barometer is used to measure atmospheric pressure." The
growth in complexity of idea is apparent.

 Sample Treatment
 Enlargement of Concepts from Primary to Upper Grades
 From
 Unit on Weather

Concepts appropriate to grades I, II, III, and IV.
1. There is air all around us.
2. Changes in air conditions make the changes in the weather.
3. Weather changes may take place rapidly.
4. Weather changes are sometimes helpful to plants and ani-
 mals, sometimes harmful.
 5. The temperature is one of the ways of describing weather.
 6. Rain, snow, hail, sleet, dry, and hot are descriptive of some
 kinds of weather.
 7. Too much rain or too little rain may be harmful.
 8. Wind is air in motion.
 9. Wind is sometimes harmful to man, sometimes helpful.
 10. Wind blows from many different directions; a wind vane
 shows the direction of the wind.

Concepts appropriate to grades IV, V, and VI.
1. Changes in weather conditions are due to natural causes.
2. Scientists use instruments in forecasting weather.
3. Our seasons are characterized by weather and climatic
 changes.
 4. Rainbows are due to the dispersion of light by water drops
 in the air.
 5. Lightning is the result of unlike electrical charges.
 6. Ocean currents affect the weather on Florida's east coast.
 7. Lakes in Florida affect the moisture and temperature con-
 ditions of the immediate surrounding country.
 8. Plants continually give up moisture to the air, and therefore
 influence weather conditions.
 9. Weather conditions at any one time for all of Florida may
 differ greatly.
10. Cold air is heavier than warm air.
11. The movement of air masses will cause changes in the
 weather.