38 



lioation in Germany, England, and the United 

 States of a pamphlet entitled "The Relations 

 of Chemistry to Agriculture, and the Agricul- 

 tural Experiments of Mr. J. B. Lawes." The 

 object of the pamphlet we will allow Liebig to 

 utate in bis own words: 



"Tho experiments of Lawes, of Rothamstead, are 

 distinguished above all others by their extent and 

 duration; and sineo the conclusions that their au- 

 thor has deduced from them stand in contradiction 

 *o the principles which I have taught in the above 

 -work, I consider his so-called practical criticism 

 of scientific views especially adapted to serve as 

 ail example to convince agriculturists how neces- 

 «iiy it is to select a correct method of experiment- 

 ing when, thereby, an opinion or doctrine is to be 

 confirmed or refuted." 



•"All- the experiments of Lawes prove precisely 

 the contrary of thai which, in his opinion, they should 

 prvve. I consider them, indeed, as the firmest sup- 

 port of the theory which they were originally in- 

 tended to combat, and the facts which lie has ascer- 

 tained, teach so many important doctrines in refer- 

 ence to the cultivation and manuring of the soil, 

 that I hold them to be of very special value to the 

 ttoory of agriculture." 



Lawes' experiments are "the firmest sup- 

 port" of the "principles" taught by Liebig, 

 and are of "very special value to the theory 

 of agriculture," and calculated to teach "im'ny 

 important doctrines in reference to the culti- 

 vation and manuring of the soil." What, then, 

 jwe the principles taught by Liebig, and what 

 .are the results of Lawes' experiments ? 



It is by no means easy to answer the first 

 question. An eminent German philosopher 

 has Kaid that Leibig's writings "swarm with 

 contradictions;" and Dr. lingo JMoIil charac- 

 terises his style as one "which leaves the reader, 

 on almost every important topic, in perfect 

 uncertainty what it really is that Liebig 

 means." 



The principal point of difference between 

 Lawes and Liebig is in regard to the so-called 

 ''mineral theory," which Mr. Lawes thought 

 embodied in the following sentence in Liebig's 

 "Chemistry in its application to Agriculture and 

 Physiology" : "The crops on a field diminish 

 or increase in exact, proportion to the diminu- 

 tion or increase of the mineral substances con- 

 veyed to it in manure." Liebig says Mr. 

 Lawes appears to be unacquainted with *any 

 other sentence in his book, "and this sentence 

 he has entirely misunderstood." Again he 

 j»js, "It is impossible to believe that he (Mr 

 Lawes) had any knowledge of this theory or 

 was acquainted with my doctrines, otherwise, 

 liow could he have declared my opinions to be 

 inconsistent with ' hi3 experimental results ?" 

 Again, "It is not difficult to refute the views 

 of another, if we attribute to him false asser- 

 tions which he has not made." Again, "That 



the mineral theory of Liebig is a pure inven- 

 i tion of Mr. Lawes' might be clear to every 

 one." Again, "My remark * * cannot bo 

 considered incorrect because Mr. Lawes has 

 misunderstood its sense." 



Leaving out of the question the work on 

 "Chemistry in its Application to Agriculture 

 and Physiology," in which Liebig now declares 

 he did not teach the "mineral manure theory," 

 let us see what he has written elsewhere, and 

 also what others, besides Mr. Lawes, havo 

 taken to be his meaning. In a letter to the 

 Revue Scicidifique ct Industrielh, Liebig says: 



"In a short time I intend publishing a work which, 

 I trust, will be interesting in the present state of ag- 

 riculture. You are aware of the great importance 

 which theoretical persons attach -to the presence of 

 ammonia in manures ; so much so, that in France 

 their value is estimated by the quantity of azote or 

 ammonia they contain. For myself, for the last three 

 years I have partaken of the common opinion, and 

 regard the azote as not only useful but also neces- 

 sary ; but my last experiment, as well as careful 

 observation, have lately compelled me to alter my 

 opinion." 



If we can understand language, Liebig here 

 plainly states, that he formerly thought ammonia 

 "not only useful but necessary," but that experi- 

 ments and observation have compelled him to alter 

 his opinion. In other words, he is now compelled 

 to thin'i ammonia neither necessary nor useful as a 

 manure. 



"It has been demonstrated," he continues "that 

 ammonia is a constituent part of the atmosphere, 

 and that as such it is directly accessible and absor- 

 bable by all plants. If, then, the other conditions 

 necessary to the growth of the plants be satisfied— 

 if the soil be suitable— if it contains a sufficient 

 quantity of alkalies; phosphates, and sulphates, 

 nothing will be wanting ; the plants will derive 

 their ammonia from the atmosphere, as they do 

 carbonic acid. We know well that they are en- 

 dowed with the faculty of assimilating those two 

 aliments; and I really cannot see why we should 

 search for their presence in iJie manures we use.''' 



In other words, if plants are supplied with their 

 appropriate mineral food, they will obtain ammo- 

 nia from the atmosphere, and we need not care to 

 apply it in manure. The following sentence also 

 indicates that Liebig considers ammonia unne- 

 cessary : 



"The question of the necessity for ammonia "m 

 our manures resolves itself into the question of the 

 necessity for animal manures, and upon the solu- 

 tion depends the entire future prospects of agricul- 

 ture; for as soon as we can dispense with bulky 

 farm-yard manure by the use of artificial prepa- 

 iations, the productive power of our fields is placed 

 in our own hands." 



In an article "On the Principles of Artifi- 

 cial Manuring," written at Gcisseo, in 1845, 

 occur the following sentences : 



"It results from this with certainty, that- the min- 

 eral substances which are furnished by the soil, 



