XXXVI 



substance is, the more effect it has ; that the yield of a field is often 

 increased merely by the addition of bone-ash rendered soluble by sul- 

 phuric acid (so-called superphosphate) ; but that above all ammonia and 

 ammoniacal salts, or, as they at last boldly stated it, combined nitrogen 

 must be added to the fields in order to secure good crops ; and for a 

 while the value of a manure was simply estimated by the amount of 

 nitrogen it contained, whereas Liebig's theory had pointed out the 

 atmosphere as a sufficient source of supply of ammonia. 



Liebig's adversaries were at this time banded together under the 

 appellation of Nitrogenists (Stickstoffler). They thought they had driven 

 Liebig for ever from the field. 



In spite of all Liebig remained true to his theory and would not yield. 

 He controverted the conclusions of Lawes and Gilbert, but without 

 success. The President of the English Agricultural Society, Pusey, 

 ranged himself distinctly on the side of Lawes and Gilbert. As the 

 masses only judge by results, the sale of the book ' Chemie in ihrer 

 Anwendung auf Agricultur und Physiologie,' which at first could not be 

 printed fast enough, became smaller and smaller, and after 1846 no new 

 edition appeared. 



In his latest writings on the subject of the mineral theory Liebig 

 acknowledged that ammonia may with advantage be supplied to cereal 

 and some other crops in the manure ; but contended at the same time 

 that it was naturally included among " mineral substances " which he 

 had originally referred to. As, however, he had clearly explained that 

 the ashes of a plant contain the mineral substances which ought to be 

 added to the soil for the growth of such plant, the statement that 

 ammonia is really a mineral compound, and ought to be included in his 

 rule regarding mineral substances, really conceded in substance the 

 argument of his opponents. 



Since the year 1845 Liebig had paid more and more attention to the 

 second part of the task which he had set himself in 1840, the application 

 of chemistry to animal physiology, and was in full work at this when 

 King Maximilian II. entered into a correspondence with him with the 

 view of calling him to Munich. Liebig had in the course of his distin- 

 guished career declined so many calls (shortly before this one a brilliant 

 call to Heidelberg), that they had little hope of persuading the eminent 

 man to come to Munich, but they induced him nevertheless. To his 

 honour be it said he did not in the least render the task more difficult 

 by great pretensions, merely stipulating that he should not be required 

 to conduct so large a laboratory as he had done at Giessen, so that he 

 might have more time for his own work. His migration took place in 

 the autumn of 1852, when in his 49th year. 



After some time he resumed at Munich his agricultural experiments, 

 and at last found out why his mineral manure had not the desired effect, 

 and why dung and even mere ammoniacal salts alone had so great an effect. 



