16 



that form the groundwork of the theory of agriculture. 

 There are other sciences, however, that have a less iolimate, 

 though not unimportant connexion with the subject. 



Almost every person, for example, has noticed how very 

 great is the influence exerted over the growth and colour of 

 plants by light. Here then we perceive a relation to the science 

 of optics. 



Gravitation also, is not without effect in giving direction to 

 the roots and branches ; though some other controlling power — 

 perhaps an instinct — must be called in to explain ail the phenom- 

 ena. 



It is well known how the produce of the soil varies with the 

 state of the atmosphere, in respect to its weight, its moisture, 

 its temperature, and purity. Hence we see how important a re- 

 lation exists between agriculture and metec roiogj^ though it 

 must be confessed that this branch of knowledge is yet extremely 

 deficient even in fundamental principles. 



The eflfect of electricity upon vegetation is much more pow- 

 erful than is generally supposed. Indeed vegetable life itself, 

 may be only a modification of this power; and it is an ingenious 

 suggestion of one of the ablest living philosophers, that those nu- 

 merous chemical changes which are constantly going on in plants, 

 may be the effect of galvanic or electrical action.* But apart 

 from Hypothesis, we have facts proving directly, thnt electricity 

 acts as a powerful stimulant to vegetation. For grain in low 

 lands, exposed to powerful storms of lightning, is thereby blight- 

 ed : and in similar circumstances buck wheat fails to be produc- 

 tive.! 



But to dwell no longer upon the theory of agriculture ; per- 

 mit me, gentlemen, by way of application of that theory (o prac- 

 tical husbandry, to make a few suggestions in regard to the mode 

 of conducting agricultural experiments. 



The frequent failure, and apparently opposite results of such 

 experiments, are facts not to be denied. Indeed, so frequent 



* Elements of the Philosophyof Plants by Decandolle and Spiengel, Sec. 

 373. 



t Same work, Sec. 372. 



