AGRICULTURAL TEXT-BOOK. 303 



(a,) That a fertile soil consists of three portions, 1. Of one which is 

 dormant, as the sand and clay which form by far the larger mass of it ; 

 2. Of the above minerals and organic matter in a state in which they 

 are insoluble in water, and therefore cannot become part of a plant ; 

 and 3. Of the same in a soluble form capable of dissolving in water, and 

 of entering into the pores of the roots. (Sec 113, p. 34.) 



(&,) That every crop which is taken off the ground carries away a 

 notable portion of the soluble materials ; and, supposing that there ex 

 isted no means of adding to them, all soil would rapidly become 

 exhausted by cultivation. 



(c.) But nature is continually rendering soluble that which she finds 

 insoluble in the soil, by the action of the air, of carbonic acid gas, by 

 heat, electricity, moisture, and complex chemical changes which are 

 always in progress. Again, a porous soil into which air and water can 

 find their way, is constantly receiving additions from the atmosphere, 

 and from spring water laden with soluble salts, raised by evaporation 

 and capillary attraction. (See $ 29, p. 9, $ 55, p. 17.) 



((/,) If, therefore, we were content to commence cultivating a virgin 

 soil, abounding in all that is requisite to form a plant ; to take off one 

 grain crop; and then leave the field uncultivated for a certain number 

 of years, we might in this manner retain the fertility of the so 1 1*1* ncl 

 at each period reap an equally large crop, for any length of time. 



(,) But this mode of cultivating the soil is unprofitable; and, there 

 fore, the ingenuity of man has discovered various modes of hastening or 

 dispensing with the action of nature. These modes are 1. A 6 re fallow, 

 where two grain crops were taken in succession, and then the laud was 

 left unfruitful for a year, but frequently plowed and stirred so as to ex 

 pose every part of it to the dissolving action of the elements. 2. Rota 

 tions, so arranged that each succeeding crop abstracted only such mate 

 rials aa were not required by the other crops ; so that when grain was 

 again sown it found an accumulation of those peculiar elements which 

 were requisite for its prosperity. 3. Draining, whereby the soil was 

 rendered porous to a considerable depth, and enabled to receive and 

 retain such elements as the air and water were capable of stipplyino-j 

 and 4. Manuring, which is procuring from some other source, and ap 

 plying directly to the soil the cle?nents necessary for the crop ; or, in 

 other words placing in the ground the raw material which nature is to 

 work up into grain ; as the paper. maker collects old rags, out of which 

 white paper is to ba nride. (See Farmer s Companion and Horticultu 

 ral Gazette, Vol. ii, p. 89.) 



(/) MANURING, therefore, may be defined to be the directly supplying 



