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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



that, above all, in order to obtain large crops, 

 ammonia, or ammoniacal salts, or, as at length it 

 was briefly called, nitrogen, must be applied, and 

 for a time the value of a manure was tested sole- 

 ly by the amount of nitrogen it contained, while, 

 according to Liebig's theory, the atmosphere was 

 the all-sufficient source of ammonia. His oppo- 

 nents rallied under the banner of this party, who 

 were called nitrogenists, and they thought that 

 they had driven Liebig forever out of the field. 



But in spite of all, Liebig remained strong in 

 faith in his theory, and would not yield to want 

 of practical success. Now and again, he entered 

 into vehement polemics, especially against the 

 validity of Lawes's experiments as opposed to 

 his theories, but without success. Pusey, the 

 President of the English Agricultural Society, 

 took the part of the practical man, Lawes, all the 

 more decidedly. 



The readers of " Chemistry as applied to Agri- 

 culture and Physiology " became fewer and fewer, 

 and after 1846 no new edition appeared. 



But it must not therefore be supposed that 

 Liebig's doctrines were refuted, for by means of 

 his numerous pupils they had made their way 

 into almost all agricultural schools, partly even 

 into practical farming. Many experiments were 

 made at the agricultural chemical stations, the 

 first of which was in Saxony, and they proved 

 more and more the correctness of the scientific 

 principles which led to the artificial manures, 

 even though they had not proved useful, and Lie- 

 big's mineral theory would have held its ground, 

 even if he had given up his researches in this 

 direction or had departed this life. But it was 

 reserved for him, with his own hand, to put the 

 keystone to the structure he had raised, and it 

 was at Munich that it was to be done. 



After 1845, Liebig had occupied himself more 

 and more at Giessen with the second part of the 

 task he had set himself, the application of chem- 

 istry to animal physiology ; and at the close of 

 1851, when I was sent by King Maximilian II. to 

 negotiate with Liebig about coming to Munich, he 

 was in the midst of these labors. He had declined 

 so many invitations that but little hope was en- 

 tertained of gaining him for Munich. We suc- 

 ceeded, however, and to his honor be it said, he 

 did not embarrass the negotiation by exorbitant 

 demands, but only stipulated that he should not 

 have the conduct of so large a laboratory as at 

 Giessen, that he might have more leisure for his 

 own pursuits. He removed to Munich in 1852, at 

 the age of forty-nine. 



After a time he resumed His agricultural ex- 



periments, and directed them to discovering why 

 his mineral manures did not produce the desired 

 effect. At length he succeeded. He proved to 

 demonstration that all cropping is robbery of the 

 soil ; that if every particle of mineral matter is 

 not restored to it by some sort of manure after 

 every crop, it is only a question of time when a 

 field will cease to be productive. 



At length it became clear to him that the 

 clods crushed by the farmer, the particles of soil, 

 play a much larger part in the nourishment of 

 plants thaa had been supposed. The idea had 

 been that besides the nourishment in the form of 

 air, that only which was dissolved in the moisture 

 contained in the soil, even if dissolved with diffi- 

 culty, contributed to the nutrition of the fruits of 

 the earth. The good effect of allowing land to lie 

 fallow was supposed to consist in the gradual de- 

 cay and solution of certain constituents, and it 

 was thought that it was only to open the soil, as 

 it was said, to make its elements soluble, so that 

 they might be sucked up by the roots of plants. 

 The growth of land-plants was supposed not to 

 differ from that of water-plants! Liebig dis- 

 covered that with field-crops, and land-plants in 

 general, it was just the reverse; that they live 

 upon matters which were once dissolved in waten 

 but again absorbed from the water by the soil 

 and rendered insoluble. He ascertained the ab- 

 sorbent power, the point of saturation, of various 

 soils for the mineral food of plants dissolved in 

 water, and found the greatest differences, not only 

 between various soils, but in the same soils for 

 various substances. He discovered, for instance, 

 that a certain quantity of ammonia, dissolved in 

 water, penetrated to a depth of ten centimetres 

 in passing through loam, an equal quantity of 

 potash to eleven, and an equal weight of phosphate 

 of lime, dissolved in water containing carbonic 

 acid, penetrated to a depth of twenty-three centi- 

 metres and a half, and saturated the soil. 



The part played by water in the soil is there- 

 fore twofold. It has not only to furnish plants 

 with their normal quantity of water, and to re- 

 store the loss by exhalation, but also to convoy 

 the nourishment to the soil from which it is ab- 

 stracted by their roots. Just as the roots are 

 able to extract the insoluble mineral matters from 

 the soil, they also extract from it moisture hygro- 

 scopically combined with it, which is then, to a 

 certain extent, restored by the atmosphere, even 

 without rain. 



The absorbent quality of the soil for matters 

 of this kind dissolved in water was not discovered 

 by Liebig ; Thomson and Way had long before 



