100 NATURE STUDY 



ing each firmly before water is poured on. Now you may come to 

 questions in regard to the percolation or retention of water falling 

 on the surface, the formation of underground reservoirs, of springs, 

 of wells, etc. 



Before studying how water rises in the soil from moist regions 

 below, some experiments in. capillary attraction would better be 

 taken up. 



Capillary Attraction. 



With a series of small glass tubes standing in a shallow dish 

 of water, observe the height the water will rise in each. Two 

 sheets of glass brought close together will show that the nearer 

 they approach, the higher the water will rise. A sponge, a cloth, 

 a lump of sugar, a piece of bread, or new brick may be used to 

 further illustrate capillary attraction. 



Arrange lamp-chimneys (or other large glass tubes) one filled 

 with gravel, one with sand, one with clay, and others with mixed 

 parts, or with any soil desired. Place them in a shallow vessel 

 of water, and observe the rising of the water in each. 



In California the rains in the winter sink down into the lower 

 depths of the soil, and in the summer with no rain, the plants 

 must depend upon this water which rises by capillary attraction 

 to the roots of the plants. 



The reason given for cultivating the orchards in the summer 

 is to break up into a loose mass the upper surface, and thus in 

 this layer destroy the conditions good for capillary attraction, 

 which, if good, would allow the water to rise to the upper surface and 

 be evaporated by the sun and thus lost. The cultivated layer of 

 soil acts as a covering retarding evaporation. To be a good cover- 

 ing it should be stirred often with the cultivator, and not allowed 

 to pack down close and thus establish good capillary connection 

 with the surface. 



