--SOIL 89 



Experiment 49. Take about a quart of soil from a few inches 

 below the surface of the ground and after sifting out the large chunks, 

 put it in a sheet iron pan and carefully weigh it to the fraction of a 

 centigram. Place the pan containing the soil in a drying oven or 

 ordinary oven, the temperature of which is but little above 100 C. 

 The soil should be spread out as thin as possible. Allow it to remain 

 in the oven for some time, until it is perfectly dry throughout. 

 Weigh again. The loss of weight will be the weight of water con- 

 tained in the soil. As there was no free water in the soil how was 

 this water held? Dip your hand into water and notice how the water 

 clings to it after it is withdrawn. Examine with the eye and the lens 

 several particles of the original soil as taken from the ground and see 

 if there is a water film on each of these as there was on the wet hand. 



Experiment 50. Take the soil after it was dried and weighed in 

 the previous experiment and heat it throughout to a red heat over a 

 Bunsen burner or in a very hot oven. Weigh again. If there is still 

 a loss of weight this must be due to the burning of the organic mat- 

 ter, rotten twigs, roots, leaves, etc., which was in the soil. Soils differ 

 greatly in the amount of water they contain and in the amount of or- 

 ganic substance present. 



We have seen from Experiment 49 how the soil takes 

 up water, and how each little particle has a film of water 

 around it. Little hairs on the plant roots are prepared 

 to take up these little films of water which surround 

 the soil particles. These water films have probably dis- 

 solved a minute amount of material from the soil particles, 

 and this material enters into the plant and can be used 

 for food. 



Experiment 51. Fill an 8 oz. bottle 

 with soil taken from a few inches be- 

 low the surface. Fit the bottle with a 

 two-hole rubber stopper having the 

 long neck of a three or four inch fun- 

 nel pushed as far as possible through 

 one hole and a bent delivery tube just Fig. 44. 



passing through the other hole. See 



that there is no air space between the soil and the stopper. The 

 soil in the bottle should be as hard packed as it was originally in 



