24 THE AMERICAN FARMER. 



cause that some soils produce crops far beyond the yield which might be reasonably looked 

 for from the fertilizing materials actually contained in them. This operation is rapidly going 

 forward during the heat of summer. The water thus charged with saline matters ascends 

 and evaporates at and below the surface, leaving them diffused throughout the soil. After 

 long-continued dry weather, a thin white coating of these salts is frequently discernible on 

 the ground. 



&quot; &quot;Where rain seldom or never falls, this result is noticeable in numerous and sometimes 

 extensive beds of quiescent (not shifting) sand. Deposits ofttimes occur several inches in 

 thickness. Such are the extensive beds of impure muriate of soda and other salts in the arid 

 deserts of Arizona; in the great Salt Lake Basin; in the southern parts of Oregon; the 

 nitrates found in India, Egypt, Peru, and various other parts of the world. 



Besides the qualitiesof soils already noticed, there are several physical conditions which 

 affect their value. They should be of sufficient depth, friable, or easily pulverized ; 

 they should possess the right color, and be susceptible of the proper admission and escape of 

 heat, air, and moisture. 



&quot; Friableness of the Soil is a quality equally removed from the adhesion of strong 

 clay or the openness of loose sand. Good loams and fertile alluvial soils always possess this 

 property. &quot;When stirred by the plow, the spade, or the hoe, the earth should fall and crumble 

 readily, although wet. Such a condition secures a ready admission to the roots, which thus 

 easily pervade the soil, and draw from it in every direction their necessary support. Under 

 draining, and the addition of coarse manures to clay, fermented manures and ashes to sand, 

 and lime and gypsum to both, will materially enhance their friableness. 



&quot; Color of Soils. Color is an essential feature in soils, and, like friableness, it has 

 an important relation to their capacity for heat and moisture. Dark-colored earths, and black 

 in the highest degree, absorb heat more rapidly than any other when exposed to a temperature 

 above their own, and it escapes with equal readiness when their relative temperature is 

 reversed. A rough, pulverized surface, which is seen in the minute inequalities of a friable 

 soil, produces the same result. During the heat of the day, especially when the sun s rays fall 

 upon the earth, the dark friable soil imbibes the heat freely, and transmits it to the remotest 

 roots, thus securing warmth to the plant, which is one of the necessary conditions of its 

 growth. When the temperature of the air falls, on the approach of evening, a reversed 

 action in the soil takes place, by which the heat as rapidly escapes. This immediately brings 

 the surface to the dew point, and secures . a copious deposit of moisture, which a friable 

 soil speedily conveys to every part of the roots.&quot; 



For reasons above given, namely, that dark soils absorb the heat more readily than 

 lighter ones, a dark soil, other conditions being equal, will be more productive than .a light 

 one. In cold climates, melons are often ripened by covering the soil an inch deep with char 

 coal dust, while it is a well-known fact that in Belgium grape-growers spread fragments of 

 black slate over their light soils, and thus greatly improve them. Muck and peat both 

 improve the soil to which they are applied, in this respect, in addition to their fertilizing 

 elements. 



The Dew Point. The temperature at which dew begins to form is called the &quot;dew 

 point,&quot; and this is a degree of temperature when the air begins to part with its vapors. It is 

 generally attained when the surface of an object is below the temperature of the air 

 surrounding it, as is often illustrated by the moisture on an earth ern, glass, or metallic vessel 

 filled with cold water on a hot summer day, or when set in a warm room in cold weather. 

 The temperature at which the vapors of the atmosphere condense to form dew is usually 

 several degrees below that of the atmosphere in clear weather, varying from four to ten 

 degrees ; but in damp or rainy weather the dew point will often be found to correspond 



