644 ANNUAL, REPORT OF THE Off. Doc. 



pulling from or robbing tlicir thicker-skinned neighbors, to be in 

 turn robbed by the neighbor next below. In this way surface ten- 

 sion aids gravity in removing water from the surface into the soil, 

 and much more rapidly than where the soil in the same mechanical 

 condition is free from moisture. It is the difference between the 

 rate at which the first rain-drop trickles down the dry glass and 

 the next one that follows in its moistened track. For this reason 

 a moist soil gets much more of a shower that gives less than an inch 

 of rain that does a dry soil, because it removes a much higher per- 

 centage of it away from the influence of the sun and wind. 



HOW THE WATER IS LOST. 



This will also explain how the water is so easily lost from the 

 soil by evaporation. When the surplus rain water is removed and 

 drainage has ceased, then the operation is reversed. The sun, wind 

 and dry air promptly attack the water films on the surface soil 

 grains, reducing their thickness. The surface films give to the air 

 and take from the soil below to make good the loss. In a short time 

 there is a continuous stream from a depth of possibly two feet to 

 the surface to make good the continual loss at that point. This up- 

 ward movement is most rapid when the films are thickest and most 

 elastic, and grows less as the films grow thinner and are held with 

 greater force against the soil surface. The manner in which this 

 loss occurs suggests the remedy or preventive. Change the moisture 

 line from the surface of the ground to a point two inches or more 

 below the surface. Do this by stirring the top soil so as to loosen 

 and dry it out. This enlarges tlPe capillary spaces and breaks the 

 films. Water cannot rise from a half-saturated soil into a dry soil. 

 Two to two and one-half inches of dry soil is a very effective mulch 

 — as good as dry straw — but needs renewing after every shower. 



Keep the surface soil dry. This is the lid to the soil cistern and the 

 stopper to the soil water-bottle. 



CONSERVATION OF MOISTURE. 



By WM. H. BLACK, Floradale, Pa. 



The increasing frequency of long periods of dry weather is suflS- 

 cient excuse for bringing this subject before you today. The aver- 

 age rainfall in Pennsylvania for a period of fifteen years has been 

 a little over three feet (38 inches). Where the annual rainfall is less 

 than two feet, agriculture without irrigation is very precarious. The 

 heaviest rainfall on the globe is on the Indian Hills facing the Bay 

 of Bengal, and averages forty-four feet per annum, but sometimes 

 reaches sixty feet. The heaviest rainfall in the United States is 

 at Astoria, Oregon, where it reaches seven feet. Sitka, Alaska, has 

 six and a half feet. 



One inch of rainfall is equal to 543 barrels of fifty gallons each, 

 or over 113 tons per acre. In one j;ear a volume of water equal to 



