46 



AGRICULTURAL CHEMISTRY. 



matter, and must be principally useful in 

 cases in which there is an excess of this 

 matter in soils. Burning, likewise ren- 

 ders clays less coherent, and in this way 

 greatly improves their texture, and causes 

 them to be less permeable to water. The 

 instances in which it must be obviously 

 prejudicial, are those of sandy, dry, sili- 

 ceous soils, containing little animal or veg- 

 etable matter. Here it only can be des- 

 tructive, ior it decomposes that on which 

 the soil depends for its productiveness. 



The advantages of irrigation, ihough so 

 lately a subject of much attention, were 

 well known to the ancients; and more than 

 two centuries ago the practice was recom- 

 mended to the farmers of our country by 

 Lord Bacon. " JVIeadow watering," ac- 

 cording to the statements of this illustrious 

 personage, (given in his Natural History, 

 in the article Vegetation,) acts not only 

 by su])pl}'ing useful moisture to the grass; 

 but likewise the water carries nourishment 

 dissolved in it, and defends the roots from 

 the effects of cold. No general principles 

 can be laid down respecting the compara- 

 tive merit of the difi'ercnt systems of cul- 

 tivation, and the different systems of crops 

 adopted in different districts, unless the 

 chemical nature of the soil, and the phy- 

 sical circumstances to which it is exposed 

 are fully known. Stiff coherent soils are 

 those most benefitted by minute division 

 and areation, and in the drill system of hus- 

 bandry, these effects are produced to the 

 greatest extent; but still the labor and ex- 

 pense connected with its application in 

 certain districts, may not be compensated 

 for by the advantages produced. Moist 

 climates are best fitted for raising the arti- 

 ficial grasses, oats, and broad leaved crops; 

 stiff, aluminous soils, in general, arc most 

 adapted for wheat crops, and calcareous 

 soils produce excellent sain-foin and clo- 

 ver. Nothing is more wanting in agri- 

 culture; than experiments in which all the 

 circumstances are minutely and scientifi- 

 cally detailed. This art will advance with 

 rapidity in proportion as it becomes exact 

 in its methods. As in physical research- 

 es all the causes should be considered^ a 

 diflference in the results may be produced, 

 even by the fall of a half an inch of rain 

 more or less in the course of a season^ or 

 a few degrees of temperature, or even by 

 a slight difference in the sub-soil, or in the 



inclination of the land. Information col- 

 lected after views of distinct enquiry, 

 would necessarily be more accurate, and 

 more capable of being connected with the 

 general principles of science; and a few 

 histories of the results of truly philoso- 

 phical experiments in agricultural chemis- 

 try, would be of more value in enlightening 

 and benefiting the farmer, than the great- 

 est possible accumulation of imperfect tri- 

 als, conducted merely in the empirical spi- 

 rit. It is no unusual occurrence for per- 

 sons who argue in favour of practice and 

 experience, to condemn generally all at- 

 tempts to improve agriculture by philo- 

 sophical enquiries and chemical methods. 

 That much vague speculation may be found 

 in the works of those who have lightly 

 taken up agricultural chemistry, it is im- 

 possible to deny. It is not uncommon to 

 find a number of changes rung upon a 

 string of technical terms, such as oxygen, 

 hydrogen, carbon, and azote, as if the sci- 

 ence depended upon words, rather than 

 things. 



But this is in fact an argument for the 

 necessity of the establishment of just prin- 

 ciples of chemistry on the subject. 



Whoever reasons upon agriculture, is 

 obliged to recur to this science. He feels 

 that it is scarcely possible to advance a 

 step without it; and if he is satisfied with 

 insufficient views, it is not because he pre- 

 fers them to accurate knowledge, but gen- 

 erally because they are more current. If 

 a person journeying in the night wishes to 

 avoid being led astray by the ignus-fatuus, 

 the most secure method is to carry a lamp 

 in his own hand. 



It has been said, and undoubtedly with 

 great truth, that a philosophical chemist 

 would most probably make a very unpro- 

 fitable business of farming; and this cer- 

 tainly would be the case if he were mere- 

 ly a pliilosophical chemist; and unless lie 

 had served his apprenticeship to the prac- 

 tice of the art, as well as to the theory. 

 But there is reason to believe that he would 

 be a more successful agriculturalist than a 

 person equally uninitiated in farming, but 

 ignorant of chemistry altogether; his sci- 

 ence as far as it went, would be useful to 

 him. But chemistry is not the only kind 

 of knowledge required, it forms a small 

 part of the philosophical basis of agricul- 

 ture; but it is an important part, and when 



