66 FRUIT-GROWING 



tremendous part in our existence which fortu- 

 nately, I suppose, we hardly realize. 



The small spaces which exist between par- 

 ticles in the soil act just as does the broken 

 thermometer tube ; they draw the moisture up- 

 ward from the supply which soaked deep into 

 the ground during the period of winter rains 

 and melting snows. If this capillarity existed 

 clear to the surface of the ground, as it does 

 when the soil becomes crusted and bakes, the 

 soil moisture would be drawn to the surface and 

 evaporated. When the surface is covered with 

 a layer of dust, the moisture works its way 

 through this dust with great difficulty and as a 

 result water is retained for the use of the trees. 



You can demonstrate this theory any morn- 

 ing at the breakfast table. Take a lump of loaf 

 sugar and place it in a saucer. Then on top of 

 the lump put a little pile of powdered sugar. 

 The lump represents normal uncultivated earth. 

 It consists of small particles of sugar more or 

 less firmly pressed together, while the pow- 

 dered sugar represents our dust mulch. Now 

 pour into the saucer a small amount of coffee 

 and watch how quickly it rises through the lump 

 until it reaches the "dust mulch." Remember 

 too that the coffee is rising not through the 

 substance of the sugar itself but through the 

 tiny spaces which exist between the individual 

 grains of sugar. You will find that it will take 



