62 PLAIN AND PLEASANT TALK 



it. If the plow begins early, and is kept going, no drought 

 likely to occur in our climate can do much injury; espe- 

 cially if the ground has been broken up deep before plant- 

 ing. 



Where the atmosphere is very dry, very hot and windy, 

 the evaporation of moisture from the plant, and from the 

 surface of the soil, is excessive. A hill of corn will exhale 

 many pounds of moisture in a day. There is no remedy 

 for excessive exhalation from plants ; but this renders it yet 

 more necessary that a supply should be kept up at the 

 roots. If the soil therefore, is permitted to evaporate from 

 its surface, the double draught upon its moisture — through 

 the plant, and from the surface — will soon exhaust its 

 water. 



Everybody knows that if a board or cloth be put upon 

 the ground, in dry weather, the earth under it will remain 

 moist — its aqueous particles being checked in their pass- 

 age upward. If a shovelful of fine manure be laid in a 

 heap upon a spot of ground, the same efiect will be pro- 

 duced. Gardeners are accustomed to cover the earth about 

 shrubs with an inch or two of fine sand ; experience teach- 

 ing them that it preserves the moisture of the soil. Now, 

 if the soil, instead of being covered with sand, or light 

 manure, be itself pulverized, the same effect will be pro- 

 duced — and for reasons which will appear. When the soil 

 is compact the moisture ascends from particle to particle 

 without obstruction. Every crevice which separates the 

 particles of earth, checks the passage of the moisture. 

 This may be more readDy seen in an analogous case — the 

 transmission of heat. Take two nail-rods, lay the end of 

 one in the fire ; divide the other into inch pieces and lay 

 them in a row from the fire, each piece touching the other. 

 The transmission of heat in the rod made up of pieces will 

 be checked at each point of division, while the uncut rod 

 will heat rapidly. On this principle, an iron chain two feet 

 long, with one end thrust into fire, will not transmit heat 



