No. 9. 



Greatest amount of Produce on a given surface. 



271 



animal body, and, as I hope, made clear the 

 distinctions between the two kinds of con- 

 stituent elements in food, and the purposes 

 they severally subserve in sustaining life, 

 let me now direct attention to a scarcely 

 less interesting and equally important sub- 

 ject — the means of obtaining from a given 

 surface of the earth, the largest amount of 

 produce adapted to the food of man and ani- 

 mals. 



Agriculture is both a science and an art. 

 The knowledge of all the conditions of the 

 life of vegetables, the origin of their ele- 

 ments, and the sources of their nourishment, 

 forms its scientific basis. 



From this knowledge we derive certain 

 rules for the exercise of the art, the princi- 

 ples upon which the mechanical operations 

 of farming depend, the usefulness or neces- 

 sity of these for preparing the soil to sup- 

 port the growth of plants, and for removing 

 every obnoxious influence. No experience, 

 drawn from the exercise of the art, can be 

 opposed to true scientific principles, because 

 the latter should include all the results of 

 practical operations, and are in some in- 

 stances solely derived therefrom. Theory 

 must correspond with experience, because 

 it is nothing more than the reduction of a 

 series of phenomena to their last cause. 



A field in which we cultivate the same 

 plant for several successive years, becomes 

 barren for that plant in a period varying 

 with the nature of the soil : in one field it 

 will be in three, in another in seven, in a 

 third in twenty, in a fourth in a hundred 

 years. One field bears wheat, and no peas; 

 another beans and turnips, but no tobacco: 

 a third gives a plentiful crop of turnips, but 

 will not bear clover. What is the reason 

 that a field loses its fertility for one plant, 

 the same which at first flourished there? 

 What is the reason one kind of plant suc- 

 ceeds in a field where another fails ? 



These questions belong to science. 



Wliat means are necessary to preserve to 

 a field its fertility for one and the same 

 plant] — what to render one field fertile for 

 two, for three, for all plants'? 



These last questions are put by art, but 

 they cannot be answered by art. 



If a farmer, without the guidance of just 

 scientific principles, is trying experiments 

 to render a field fertile for a plant which it 

 otherwise will not bear, his prospect of sucj- 

 cess is very small. Thousands of fiirmers 

 try such experiments in various directions, 

 the result of which is a mass of practical 

 experience forming a method of cultivation 

 which accomplishes the desired end for cer- 

 tain places; but the same method frequently 

 does not succeed — it indeed ceases to be ap- 



plicable to a second or third place in the im- 

 mediate neighbourhood. How large a capi- 

 tal, and how much power, are wasted in 

 these experiments ! Very different, and far 

 more secure, is the path indicated by sci- 

 ence; it exposes us to no danger of iailing, 

 but, on the contrary, it furnishes us with 

 every guarantee of success. If the cause 

 of failure — of barrenness in the soil for one 

 or two plants — has been discovered, means 

 to remedy it may readily be found. 



The most exac^ observations prove that 

 the method of cultivation must vary with 

 the geognostical condition of the subsoil. 

 In basalt, greywacke, porphyry, sandstone, 

 limestone, &c., are certain elements indis- 

 pensable to the growth of plants, and the 

 presence of which renders them fertile. 

 This flilly explains the difference in the 

 necessary methods of culture for different 

 places; since it is obvious that the essential 

 elements of the soil must vary with the va- 

 rieties of composition of the rocks, from the 

 disintegration of which they originated. 



Wheat, clover, turnips, for example, each 

 require certain elements from the soil; they 

 will not flourish where the appropriate ele- 

 ments are absent. Science teaches us what 

 elements are essential to every species of 

 plants by an analysis of their ashes. If, 

 therefore, a soil is found wanting in any of 

 those elements, we discover at once the 

 cause of its barrenness, and its removal 

 may now be readily accomplished. 



The empiric attributes all his success to 

 the mechanical 6perations of agriculture: 

 he experiences and recognises their value, 

 without inquiring what are the causes of 

 their utility, their mode of action: and yet 

 this scientific knowledge is of the highest 

 importance for regulating the application of 

 power and the expenditure of capital — for 

 insuring its economical expenditure and the 

 prevention of waste. Can it be imagined 

 that the mere passing of the ploughshare or 

 the harrow through the soil — the mere con- 

 tact of the iron — can impart fertility miracu- 

 lously? Nobody, perhaps, seriously enter- 

 tains such an opinion. Nevertheless, the 

 ■modus operandi of these mechanical opera- 

 tions is by no means generally understood. 

 The fact is quite certain, that careful 

 ploughing exerts the most favourable influ- 

 ence ; the surface is thus mechanically di- 

 vided, changed, increased, and renovated ; 

 but the ploughing is only auxiliary to the 

 end sought. 



In the effects of time, in what in agricul- 

 ture are technically called fallows — the re- 

 pose of the fields — we recognise by science 

 certain chemical actions, which are continu- 

 ally exercised by the elements of the atmos- 



