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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



pure science for the widest circle of readers. 

 They are also indispensable to the expert, for the 

 author constantly used them, as he himself stated, 

 to illustrate his views on chemistry, agriculture, 

 and physiology. He expended great pains upon 

 them. Not long before his death, he wrote to 

 one of his pupils who had published a small pop- 

 ular work : 



" The style of your book is excellent ; it is 

 really a masterpiece of simplicity and clearness. 

 To most readers it may appear off-hand, as many 

 have said of my chemical letters, but I am sure 

 that you have expended much care and attention 

 on the composition, as I did on mine ; there is an 

 art in simplicity and freshness of style which, 

 however, must be kept out of sight." 



Liebig thus gave the highest praise that he could 

 bestow on a popular work. 



It was the comprehensive view which Liebig 

 took of chemistry which naturally turned his at- 

 tention to agriculture and animal physiology. 

 Having devoted more attention than any other 

 chemist to the materials of organic Nature, he 

 wanted to observe them in the laboratories in 

 which they were produced, to study the part they 

 played in the economy of Nature. It is well 

 known that he became a pioneer in these depart- 

 ments and gave a great impetus to the study of 

 them. I will confine myself to the mention of a 

 few of the chief points. 



What is called Liebig's agricultural chemistry 

 may be divided into two periods — the first from 

 1840 to 1846 at Giessen, the second from 1866 to 

 1862 at Munich. His researches in vegetable 

 and animal physiology were first made known in 

 a work which appeared in 1840, called "Chem- 

 istry as applied to Agriculture and Physiology." 

 This step involved so many consequences that I 

 must enter a little further upon the subject. 



In 1837, at the meeting of the British Asso- 

 ciation held at Liverpool, Liebig was requested to 

 draw up a report on the existing state of knowl- 

 edge of organic chemistry. He consented, but 

 proposed that the French chemist, Dumas, should 

 join him in the work. Dumas, however, does 

 not seem to have agreed, and in 1840 Liebig's 

 book appeared. It met with unusual success ; 

 six editions were called for in six years, and it 

 excited great attention, so great that in 1841 

 Dumas felt constrained to put forth something 

 similar in French, and formally indorsed Liebig's 

 main principles, although some of them were much 

 disputed. He said, "Elles appartiennent a notre 

 ecole, dont l'esprit est venu s'exercer sur ce ter- 

 rain nouveau." 



But the success of the book in another re- 

 spect was not so great — in its effect at first upon 

 agriculture and physiology and their representa- 

 tives. They almost all regarded Liebig, with his 

 notions and theories, as an interloper, who must 

 be driven back into his own territory ; and a con- 

 test began. Even some distinguished chemists 

 did not approve of Liebig's having, like an ambi- 

 tious ruler, thus extended his domain. Berzelius 

 from the first was doubtful, and a few years later 

 was quite at enmity with Liebig about these 

 theories of probability, as he called the applica- 

 tion of chemistry to things of this sort. In his 

 annual report of 1841, Berzelius said of Liebig's 

 book, that it was written with all the ability to 

 be expected from so distinguished an author, but 

 made no secret of his opinion that Liebig had 

 erected a structure that was already tottering to 

 its fall. 



The more critical, and even hostile, was the 

 attitude of the agriculturists, physiologists, and 

 chemists, the louder was the applause of the 

 public at large ; but whether it was entirely satis- 

 factory to Liebig I cannot say, for no one of the 

 applauding multitude could bring Berzelius to 

 another mind, invalidate the experiments of Bra- 

 connot, or the objections of Boussingaidt, could 

 convince the skeptical farmers, or put the polem- 

 ical physiologists to silence. It appears to me 

 that Liebig must have felt rather isolated at this 

 period, for even his best friends saw that in the 

 lofty flights to which his imagination had led 

 him he had often asserted more than he had 

 proved, and that the prosaic task of proof had 

 yet to be entered upon. He had thus raised up 

 a host of opponents who were by no means to be 

 despised, and was left to his own resources in 

 dealing with them. The way in which he suc- 

 ceeded, in course of time, is worthy of all admi- 

 ration. 



At the time when Liebig was called upon to 

 undertake the work which caused so much ex- 

 citement, his powers were in their prime. When 

 such a man as he was takes a general survey of 

 things, his field of vision may be expected to 

 extend beyond the usual range. What was the 

 main thing that Liebig discovered ? 



He never claimed to be the first to make 

 chemical experiments in agriculture. On the 

 contrary, in the dedication of his book to Alex- 

 ander von Humboldt he says : 



" There is one part of the little book which I 

 take the liberty of dedicating to you, of which I 

 scarcely know whether it is really mine. When 

 I read your introduction to Ingenhouss's work on 



