On Afjricultural Chemistry. 



229 



priety in an inJependent work. The views which I have adopted, 

 and which I shall now endeavour to explain, have arisen durins: 

 the course of these experiments ; but it is very probable I shall 

 have reason to modify them as the inveslijjation proceeds. 



I certainly place great reliance on the experimental results 

 which I possess ; every operation has been conducted under the 

 eye of Dr. Gilbert, a gentleman who received his scientific edu- 

 cation in the best British and continental laboratories^, and has 

 applied that accuracy which modern science demands, both to the 

 operations of the laboratory and the field. 



In the first place I shall offer some general remarks upon the 

 growth and nature of the common agricultural plants, and after- 

 wards endeavour to show the effect of manures upon them. 



The crops which form a rotation belong, botanicallv speaking, 

 for the most part to the three following natural orders of plants : — 

 The Graminece, containing wheat, barley, oats, rye, and the 

 grasses which constitute our natural pastures ; the LegximinoscB, 

 containing beans, peas, tares, lucerne, clover, trefoil, saintfoil, 

 &c. ; and the Cruciferce, containing turnips and rape. The 

 Solanece, yielding the potato, and the Umlelliferce, carrots and 

 parsnips^ ma ay also be noticed. For the purposes of agriculture, 

 however, a different system of classification might be adopted with 

 advantage, having reference to the organ or part of the plant which 

 is the object of cultivation. In clover, tares, and pasture, we 

 generallv require leaf and stem, which may be termed the primary 

 organs of plants ; in the turnip we require the bulb or intermediate 

 organ; and in the grain crops, peas, beans, <S:c., the ultimate 

 organ, the seed. 



In considering this subject it is necessary to bear in mind that 

 the natural aim of every plant is to produce a perfect seed, and 

 that, when growing in a soil and climate adapted to its special 

 habits and peculiarities, it produces no more of each organ than it 

 requires for the healthy perpetuation and reproduction of seed. 

 When the leaf has fulfilled its ofhce, the nutritious fluids circu- 

 lating through it are withdrawn, and it decays or dries up. 

 These fluids enter into the stem, and, rising higher and higher, 

 are at length deposited in the seed. Plants are therefore required 

 bv ag-riculturists in two distinct conditions, one in which the 



J c> _ .... 



nourishment is more or less circulatory, the other in which it is 

 fully elaborated and deposited: in one case water constitutes 

 above three-fourths of the weight of the produce ; in the other it 

 does not generally amount to one-fifth. Although the agricul- 

 turist possesses the means of developing the circulatory or elabo- 

 ratory conditions of plants by manures and mechanical operations, 

 climate exerts the greatest influence over them. By climate I 

 mean the quantity of rain that falls, the number of days on which 



