46 BOARD OF AGRICULTURE. 



It contains accounts of numerous rude chemical experiments, 

 all of which go to prove that the author was no chemist. 

 There are, however, some practical facts contained in the 

 volume, which were of no inconsiderable value, if they were 

 understood and heeded by the farmers of that age. 



Among the names of those conspicuous for researches in 

 the field of organic chemistry at the commencement of the 

 present century are those of Davy and Berzelius ; but they 

 fell into errors, and their deductions are so erroneous, they 

 serve to show how very imperfect and incomplete the sciences 

 were fifty or sixty years ago. 



It was not until the advent of Liebig that the cloud of 

 error was dissipated, and the doubts and uncertainties which 

 surrounded the subject were removed. He showed very 

 clearly how plants obtained their food, what were the sources 

 whence they derived the elements, and the nature of the 

 office performed by manures. He gave the results of care- 

 ful experimental labors which supported the correctness of 

 his statements ; and most of his deductions stand to-day as 

 demonstrated truths. Prior to his time, it was generally 

 supposed by chemists that plants derived their carbon from 

 the soil, although it must be stated tliat Priestley and Ingen- 

 housz quite early adopted the view that it was suj)plied by 

 the air. It was deemed impossible that plants could possess 

 the capability of exerting a decomposing force in the separa- 

 tion of carbon from oxygen greater than could be produced 

 in the laboratory, with the aid of powerful acids and intense 

 heat. Liebig, however, established the fact on a firm basis, 

 that the largest portion of plants, the carbon, is elaborated 

 from the invisible atmosphere, and, without its agency, no 

 plant-life could exist. 



The element nitrogen was a stumbling-block in the way 

 of the early chemists ; and they were unable, with their 

 imperfect methods of analysis, to detect its presence in 

 plants. Liebig demonstrated that it always exists in the 

 same proportion in certain constituents of plants, and the 

 substances containing it are those which form the most 

 valuable part of food. He showed the sources from which 

 this most important element is derived ; or, at least, in his 

 early work, " Organic Chemistry applied to Agriculture," he 

 points out the agents through which it is supplied in the 



