J. B. LAWRS AND JUSTUS VON LIEBIG. 



239 



vation, have lately compelkal me to alter my opinion." 



"It has been demonstrateil that ammonia is a con- 

 stituent part of the atmosphere, anil that as such it 

 is tlircctly accessible and absorbable by all plants. 

 If, then, the other coniiitions necessary to the growth 

 of the plants be satisfied — if the soil be suitable — if 

 it contains a sudicient quantity of alkalies, phos- 

 phates, and sulphates, nothing will be wanting; the 

 plants will derive their ammonia from the atmos- 

 phere, as they do carbonic acid. We know well 

 that they are endowed with the faculty of assimila- 

 ting those two aliments; and I really cannot see why 

 we should search, for their presence in the manures 

 U'e vse." 



"The question of the nece.sssity for ammonia in our 

 manures resolves itself into the question of the neces- 

 sity for animal manures, and upon the solution de- 

 pends the entire future prospects of agriculture; for 

 as soon as we can dispi'iise with bulky farm-yard ma- 

 nure by the use of ariilii'ial preparations, the pro- 

 ductive power of our fields is placed in our own 

 hands." 



In an article " On the Principles of Artificial Ma- 

 nuring," written at Geissen, in 1845, occur the follow- 

 ing sentences : 



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

 eral substances which are furnished by the toil, and 

 which are found again in the ashes of plants, are 

 their true food; that they are the conditions of veg- 

 etable life.'' 



"The fertilizing power of manure can be deter- 

 mined by weight, as its effect is in direct ratie to its 

 amount in the mineral elements of the food of plants." 



" If these elements (the ashes of plants) are pres- 

 ent in sufficient quantity and in appropriate propor- 

 tions, the soil contains the conditions which render 

 the plant capable of absorbing carbonic acid and 

 ammonia from the air, which is an inexhaustible 

 storehouse for them, and renders]] their elements ca- 

 pable of being assimilated by their organism." 



" If we do not restore to a meadow the elements 

 withdrawn, its fertility decreases. But its fertility 

 remains unimpaired, with a due supply of animal ex- 

 crements, fluid and solid, and it not only remains the 

 same, but may be increased by a supply of mineral 

 substances alone, such as remain after the combus- 

 tion of ligneous plants and other vegetables, namely, 

 ashes. Ashes rep.-esent the whole nourishment which 

 vegetables receive from the soil. By furnishing them 

 in sufficient quantities to our meadows, we give to 

 the plants growing on them the power of condensing 

 and ab:^orbing carbon and nitrogen by their surface." 



Must not, we ask, the effect of the solid and fluid 

 excrements, which are the ashes of plants and grains 

 burned [the italics are Liebios] in the bodies of an- 

 imals and of man, be dependent upon the same cause? 



Must not the fertility resulting from their application 

 be, to a certain extent,* independent of the ammonia 

 they contain? Would not the effect be precisely the 

 same in promoting the fertility of cultivated plants, 

 if we had evaporated the urine and dried and burned 

 the solid excrements before adding them to the soil? 

 Surely the cerealia and leguminous plants which we 

 cultivate must derive their carbon and nitrogen from 

 the tame source whence the graminea and legumin- 

 ous plants of the meadow obtain them. No doubt 



can be entertained of their capability to do so." 



Letters on Chemistry, last London edition, page 514. 



" Nothing can be more certain than the fact that 

 an exportation of nitrogenized products does not ex- 

 haust the fertility of a country ; inasmuch as it is 

 not the soil, but the atmosphere which furnishes its 

 vegetation with nitrogen. It follows, consequently, 

 that we cannot increase the fertility of our fields by 

 a supply of nitrogenized products or hj salts of am- 

 monia alone ;t but rather that their produce in- 

 creases or diminishes in a direct ratio with the sup- 

 ply of mineral elements capable of assimilation. 

 * * * If we supply along with the ammonia all 

 the conditions necessary for its assimihition, it minis- 

 ters to the nourishment of the plants; but if this ar- 

 tificial supply of ammonia is not given, they can de- 

 rive all Ike required nitrogen from the atmosphere." 

 —Ibid 517. 



These quotationa require no comments. Mr. 

 Lawes is severely censured for supposing that Liebio 

 taught that theory which ascribes the effect and val- 

 ue of manures to the inorganic constituents of plants 

 which they contain. Liebio thinks Mr. Lawes has 

 read only one sentence of his book, and misunder- 

 stood that one. Let us see, therefore, what otheis 

 have understood Liebio to mean. 



Sullivan, in his Manures of the Farm, says : 

 "The admixture of caustic Hme with night soil has 

 been objected to on the ground of the chemical de- 

 composition which would thereby ensue, and the con- 

 sequent evolution and waste of ammoniacul gas; but 

 we have the high authority of Liebio for staling 

 that the efficacy of human focees as manuie does not 

 depend on their ammonia or nitrogen. Ileuce, in 

 depriving night soil of smell, we do not diminish its 



* We are now quoting from the last edititm cf LlEBlG's Famil, 

 iar Letters on Chemistry, publif^hed in 1H5L subsequent to the 

 publication of Mr. Lawes' results. TAtg qualifying dauaetttutujl 

 in tltefiyrmtT editioTS, where the xtintfuce reads *'Soould not Uw 

 fertility resulting from their application be altvgtther independent 

 of the ammonia they contain r" 



■f Here, again, this qualifying clause was not in the former edi- 

 tions, which read— "We cannot increese Ihe feitilily of our BeMi 

 by a tupply of nitrogenized manure, orhy salts of ammonia." The 

 change of the word manure to product* U also significaut. 



