STATE AGRICULTURAL SOCIETY. 107 



one-half inch in diameter, the surface of the liquid will be curved 

 or concave. In a very narrow tube the liquid will rise to a con- 

 siderable height. In these cases the surface attraction of the 

 glass for the water, neutralizes or overcomes the weight of (earth's 

 attraction for) the latter. The pores of a sponge raise and hold 

 water in them, in the same way that these narrow (capillary*) 

 tubes support it. When a body has pores so fine (surfaces so 

 near each other,)that their suiface attraction is greater than the 

 gravitating tendency of water, then the body will suck up and 

 hold water, will exhibit capillarity; a lump of salt or sugar, a 

 lamp wick, are familiar examples. When the pores of a body 

 are so large, (the surfaces so distant) that they cannot fill them- 

 selves, or keep themselves full, the body allows the water to run 

 through or to percolate. 



Sand is most easily permeable to water, and to a higher degree, 

 the coarser its particles. Clay on the other hand is the least 

 penetrable, and the less so, the purer and more plastic it is. In 

 an agricultural sense, sand implies those coarse particles or grains 

 whose form can be defined by the eye, while all the finer impal- 

 pable portions of a soil, though consisting in part of very fine 

 grains of sand, may be called clay. The chemist, however, 

 understands by clay a definite chemical compound. This dis- 

 tinction should ])e borne in mind. Sand, i. e. grains of quartz, 

 or undecomposed rock, may be made so fine, that with the admix- 

 ture of a little true clay, it opposes the passage of water to a 

 considerable extent. 



When a soil is too coarsely porous, it is said to be leachy or 

 hungry. The rains that fall upon it, quickly soak through, and 

 it shortly becomes dry. On such a soil, the manures that may 

 be applied in tlie spring, are to a great degree washed down below 

 the reach of vegetation, and in the droughts of summer, plants 

 suffer and perish from want of moisture. 



When the texture of a soil is too fine, its pores too small, as 

 hapjK'ns in a heavy clay, the rains penetrate it too slowly; they 

 flow off' tlie surface, if the latter be inclined, or remain as ])ools 

 for days and even weeks, in the hollows. 



In a soil of proper texture, the rains neither soak off' into the 

 under earth, nor stagnate on the surface; but the soil always 



• From capillua the Latin word for hair, because m fine m a hair, (but a hair is no tube, ag 

 U often suiiposcd.) 



