On the Great or Jersej/ Trench-P/ougli. 45 



whole human species^ the riches of states, and all commerce. 

 There is no other profession in which the application of correct 

 principle is productive of more beneficial effects, or is of greater 

 and more decided influence. Hence it appears quite unaccount- 

 able that we may vainly search for one leading principle in the 

 writings of agriculturists and vegetable physiologists." 



Further on : " It is the greatest possible mistake to suppose 

 that the temporary diminution of fertility in a soil is owing to the 

 loss of humus : it is the mere consequence of the exhaustion of 

 the alkalies. For small as is the quantity of alkali which plants 

 require, it is nevertheless quite indispensable for their perfect 

 development. But when one or more years have elapsed without 

 any alkalies having been extracted froin the soil, a new harvest 

 may be expected." 



How may I practically apply this ? Twenty years since an old 

 experienced farmer observed to me : — " You do not use vraic 

 (kelp-ashes) ; try them ; put 21. 5s. worth of ashes per acre on 

 your land prepared for wheat, let it lie on the surface a month or 

 two, and turn it in with your wheat ; it will return you 3/. or 4/. 

 profit, with a finer sample; it makes grain, or fills the ear well." 

 The result has fully justified the prediction. It has been the 

 constant practice in Jersey for a century past, and does precisely 

 act as Liebig states. He observes, p. 152: — '•' Wheat will not 

 grow on a soil which has produced wormwood, and, vice versa, 

 wormwood does not thrive where wheat has grown, because they 

 are mutually prejudicial, by appropriating the alkalies of the soil." 

 Again, p. 161 : — " It was deduced from all the foregoing facts, 

 that plants require for their growth different constituents of soil, 

 and it was very soon perceived that an alternation of the plants 

 cultivated maintained the fertility of a soil quite as well as leaving 

 it at rest or fallow. It was evident that all plants must give back 

 to the soil in which they grow different proportions of certain sub- 

 stances, which are capable of being used as food by a succeeding 

 generation. 



" Now as excrements cannot be assimilated by the plant which 

 ejected them, the more of these matters which the soil contains, 

 the more unfertile must it be for plants of the same species. 

 These excrementitious matters may, however, still be capable of 

 assimilation by another kind of plants, which would thus remove 

 them from the soil, and render it again fertile for the first. And 

 if the plants last grown also expel substances from their roots, 

 which can be appropriated as food by the former, they will improve 

 the soil in two wajs. When we grov/ in the same soil for several 

 years in succession different plants, the first of which leaves 

 behind that which the second, and the second that which the third 

 may require, the soil will be a fruitful one for all the three kinds 

 of produce. If the first plant, for example, be wheat, which con- 



