LIEBIG'S SCIENTIFIC ACHIEVEMENTS. 



69 



'The Nourishment of Plants' of forty-two years 

 ago, it always appears to me as if I had hut carried 

 out and tried to prove the views, therein expressed, 

 of the most eminent naturalist of this century." 

 What was it, then, which occasioned all this com- 

 motion ? 



In my opinion, it was not the facts adduced, 

 which were mostly known before, but the idea 

 by which Liebig's mind was so possessed, that, 

 of all life upon earth, vegetable life alone has 

 any affinity with lifeless, inorganic Nature ; that 

 vegetable life, by the aid of inorganic mineral 

 matters, forms new and complex forms of organic 

 Nature ; that animal life derives its life solely 

 from vegetable life, and the animal, under the 

 influence of the oxygen which it inhales, again 

 resolves these combinations into the simple, inor- 

 ganic mineral matters, carbonic acid, hydrogen, 

 ammonia, etc., out of which vegetable life com- 

 bined them by the separation of oxygen in the 

 air. It was this simple rotation of matter in 

 animated Nature which excited Liebig and others, 

 and it soon found favorite popular illustration in 

 the little aquariums which were called " Liebig's 

 World in a Glass Case." 



Liebig embraced this idea enthusiastically, and 

 it raised him to a height from which prospects 

 opened out before him as yet concealed from oth- 

 ers, and it induced him to publish many things 

 which, having been seen only afar off, wore a dif- 

 ferent aspect when viewed more closely. He be- 

 gan to bear down all obstacles in his path at the 

 risk of being considered a ruthless destroyer. 



The method pursued by Liebig in his agricult- 

 ural chemistry was slow and laborious ; it would 

 have taken any one else three times as long. The 

 first great task was the examination of as great a 

 variety of plants as possible from various places, 

 their component parts, and those of their ashes. 

 He did not place much value on analysis of soils, 

 which had been considered so important, espe- 

 cially how much humus a soil contained ; what 

 he wanted to know was the effect of every plant 

 on the soil on which it grew. It was soon found 

 that the ashes of all plants yield qualitatively the 

 same mineral constituents, but that every species 

 yields its own peculiar ashes, for different species 

 growing side by side on the same soil absorb its 

 mineral elements in very different proportions. 



Liebig sent out letters asking for analysis of 

 ashes in all directions ; and, in order to facili- 

 tate the task, his assistants, Will and Fresenius, 

 worked out and published an excellent method of 

 obtaining them. In a comparatively short time 

 thousands of results were obtained. 



Liebig now put into practice the results of 

 the discovery that every species of plant takes 

 from the soil a certain quantity of mineral matter, 

 in certain combinations, which is found in their 

 ashes ; and his opinion that plants derive the rest 

 of the material required for their growth from 

 the atmosphere, in the form of carbonic acid, 

 hydrogen, and ammonia, by the aid of their 

 leaves and roots. He asserted that, in order to 

 make a cornfield perpetually productive, you 

 have only to restore to it the mineral matters 

 withdrawn from it by the harvest ; the atmos- 

 phere and the conformation of the soil, regulated 

 by the mechanical part of farming, will take care 

 of the rest. 



A soda-manufacturer at Liverpool was com- 

 missioned by Liebig to make arrangements for 

 supplying the farmers with mineral manures for 

 wheat, rye, oats, clover, potatoes, etc. They were 

 prepared according to a method invented by Lie- 

 big, the essential feature being that the nourish- 

 ing salts, too readily soluble in water, were made 

 less soluble by being mixed with carbonate of 

 lime, that they might not be carried off by the 

 rain out of reach of the sprouting seeds. 



Liebig was thoroughly convinced of the cor- 

 rectness, of his mineral theory, and as thoroughly 

 of the efficacy of his mineral manures. It did 

 not, however, turn out as he expected. His gen- 

 ius was to be sharply put to the test. 



The English farmers found no result from the 

 artificial manures, left off buying the useless stuff, 

 returned to their old manures, and the works at 

 Liverpool were given up. Indeed, Liebig was 

 compelled to admit, from his own farming experi- 

 ments at Giessen, that his mineral manures did 

 not render a sterile soil essentially more fertile. 

 One ray of hope appeared after years of non- 

 success ; the crops obviously increased a long 

 time after they had been manured. But this was 

 only another puzzle. 



Meanwhile, all his opponents bestirred them- 

 selves, not only to demonstrate the uselessness 

 of mineral manures, but to upset the mineral 

 theory altogether, and to show that, in order to 

 obtain practical results in farming, you must go 

 to work in an entirely different way. First and 

 foremost was an English land-owner, Mr. Lawes, 

 who, together with a chemist of the name of Gil- 

 bert, made experiments with various manures 

 which they manufactured. It was shown that 

 the more soluble a manure is, the greater the 

 effect produced, that the produce of a field of- 

 ten increases enormously if only common salt 

 be put upon it, especially superphosphate ; but 



