46 AMERICAN AGRICULTURE. 



CRUSHED MICA, FELDSPAR, LAVA, THE TRAP ROCK3, &c. 



Feldspar contains 66.75 of silica; 17.50 alumina; 12 potash; 

 1.25 lime ; and 0.75 oxide of iron. Mica consists of silica, 

 46.22 ^ alumina, 34.52; peroxide of iron, 6.04; potash, 

 8.22; magnesia and manganese, 2.11. Most of the lavas and 

 trap-rocks hold large quantities of potash, lime, and other 

 fertilizing ingredients. The last frequently form the entire 

 soils in volcanic countries, as in Sicily, and around Mount 

 Vesuvius in Italy, in the Azores and Sandwich Islands ; and 

 their value for grains and all cultivated plants is seen in the 

 luxuriance of their crops and the durability of their soils. 

 These examples illustrate the great influence of saline ma- 

 nures, and their near approach to an entire independence in 

 sustaining vegetation. Whenever they become exhausted by 

 the severe usage they undergo, two or three years of rest ena- 

 bles them again to .yield a remunerating crop to the improvi- 

 dent husbandman. Granite, sienite, and some other rocks, 

 yielding large proportions of potash and some lime, abound 

 throughout the eastern portion of this country. The potash 

 in them is however firmly held in an insoluble state ; but if it 

 be subjected to a strong heat, it may afterwards be crushed, 

 and then yield it in an easily soluble form, and constitute a 

 valuable top-dressing for lands. 



It is a subject of frequent remark, that the soil underneath, 

 or in immediate contact with some stone walls, which have 

 been erected for a long period, is much richer than the adjoin- 

 ing parts of the same fields. This difference is probably 

 due, in some measure to the slow decomposition of important 

 fertilisers in the stone, which are washed down by the rains 

 and become incorporated in the soil. The removal of stones 

 from a fertile field, has been deprecated by many an obser- 

 ving farmer, as materially impairing its productiveness. Be- 

 yond the shade thus afforded against an intense sun, protection 

 from cold winds, their influence in condensing moisture, 

 (and the beneficial effects which perhaps ensue as injibrous cov- 

 ering,) the difference may be attributable to the same cause. 



SPENT LYE OF THE ASHERIES 



Is the liquid which remains after the combination of the 

 lye and grease in manufacturing soap. It is of great value 

 for plants. Before its application to the land it should be 

 mixed with peat or turf, or diluted with ten times its bulk of 

 water. Five gallons of this lye is estimated to contain as 



