148 ANALYSIS OF SOILS. 



the pines. Those of the oak contain 5 per cent, of saline and earthy 

 matter, while the fir tribe afford only about 2. The improvement, 

 therefore, is in proportion to the quantity and kind of inorganic matter 

 trees receive from the air. This determines also the kind of passes 

 which will be produced. Lands laid down with artificial grasses for 

 a few years are better fitted for grain crops ; but they deteriorate after 

 this time, it is believed, if kept in these grasses. They will not im- 

 prove beyond a certain extent, any more than they will with any other 

 crops. Old and extensive commons, heaths and wastes are evidences 

 in point. But some grass-lands retain their good condition for a long 

 period without manuring, as some rich grain-lands have for a century. 

 Any improvement that takes place is in the formation of a dark-brown 

 surface-soil, imbued with vegetable matter, and which becomes thicker 

 in proportion to the time it has laid down to grass. The thickening 

 however sooner ceases if the soil be light and sandy; if moderately 

 heavy, the improvement continues longer, and if somewhat clayey, it 

 may be made permanently good. 



The analysis of the best pasture lands shows that they contain from 

 8 to 12 per cent, of organic matter, mostly vegetable; from 5 to 10 of 

 alumina, and from 1 to 6 of lime. If but a 10th part of the grass dies 

 annually on the soil, in the state of roots and stubble, vegetable mat- 

 ter must increase, in time, to a very considerable amount, while arable 

 land cannot be improved from this circumstance, as it is constantly 

 turned up with the vegetable remains. The leaves and roots of the 

 grasses contain inorganic and saline matter ; and dry hay, when 

 burned, yields 8 or 10 per cent, of its weight of ash, so that, beside 

 the vegetables left in the soil, a fine earthy powder is formed, which is 

 the cause of the fineness of the surface of old grass fields, consisting 

 mostly of lime and silica, and differing from the clay soil originally 

 and now below. Clay soil is also modified by the roots of grasses 

 penetrating it, and opening a way for the rains, which carry down the 

 clay with them. Thus changes in the character of soils constantly 

 take place. Soils which are light contain little clay, and the grasses 

 therefore thrive more rapidly, and a thicker sward is sooner formed ; 

 but the rains wash out the clay and they do not form permanent pas- 

 ture lands, as with clay soils. If the old pasture lands are ploughed 

 up, many years will be required to effect the same condition as that 

 before, as the lower soil is mixed up with the fine mould of the surface, 

 and the vegetable matter disappears by rapid decomposition. At first 

 the sowing down of natural grasses on heavy land will often disap- 

 point expectations ; and on light and loamy lands, a thick sward can- 

 not well be expected ; but in time both soils may be improved. 



The quality and quantity of grain depend upon the means adopted 

 to improve the soil. Flour made into dough and washed with water 

 on a linen cloth, as long as the water passes the milky flour through, 



