WATER. 



Im- 



pacting is prevented ; mellow soil retains moisture better 

 than packed soil. The circulation of air in the soil returns 

 ammonia to it, stimulates chemical changes that contribute to 

 plant growth and nourishes nitro-bacteria, but these important 

 facts cannot be taught experimentally at this stage. 



Encourage observation of drain-making. Have pupils learn 

 how the digger determines the slant in the bottom of the 

 drain to make a proper fall for the water. The channels may 

 be made of tiles or stones or wood. If convenient, visit a 

 drain-maker at work. A teacher, assisted by his pupils, in 

 Lambton County tile-drained the school yard into a road-side 

 ditch. 



Correlate Observation with Experiment. — As has been 

 already stated experiments should not be made merely for 

 the sake of making them. The need for an experiment on 

 soil should arise naturally in some study or discussion of plant 

 life. It should seek to answer a question and, when successful, 

 should be applied in as many ways as can be conceived. The 

 need for an experiment may create the need for, and may 

 maintain interest in, a series of which it may be near the 

 beginning, middle or end. A need does not usually arise by 

 accident ; the skilful teacher anticipating it, selects a path that 

 leads his pupils, unwittingly it may be, to the issue he desires. 

 Experiment and observation should mutually reinforce each 

 other. While the experiments with soils in fruit-cans are in 

 progress their correlatives, taking place on a large scale on the 

 adjoining farms, should be observed and discussed. 



Water. — The Volume of Equal Weights of Water and Ice. 

 A glass bottle filled with water has been burst by the frost, 

 hence the opportunity to introduce the lesson. 



What follows when a water-soaked porous rock is subjected 

 to hard frost % In another lesson it was seen that soil may be 

 produced by such action. 



