CHEMICAL MANURES. 33 



combined action of the humus and carbonate of lime. But in what 

 is the favorable action of the humus manifest ? Is it because of its 

 absorption under the form of humus ? No. Its part is limited to 

 favoring the dissolution of the carbonate of lime ; and to prove it, it 

 is sufficient to make a fifth experiment, in which we replace the car- 

 bonate of lime and humus by sulphate -of lime, -or, better still, by 

 nitrate of lime, which is much more soluble, to see another return 

 of 1.3 ounces or 558 grains. It is useless to add that when we em- 

 ploy nitrate of lime, it is with regard to the azote it contains, and 

 that it enters in with the azotic matter. Thus is demonstrated by in- 

 disputable experiments that the good effects of the humus are due, in 

 this case, to the dissolvent action upon the lime ; and what proves it is 

 the possibility of arriving at the same result by the aid of the salt 

 of lime, which is more soluble than the carbonate. I will even tell 

 you that it is this which has determined me to substitute the sulphate 

 for the carbonate of lime in the composition of the complete manure. 



But you will say, These are the experiments of the laboratory, and 

 in matters of agriculture it is often dangerous to abide by such testi- 

 mony. You ask me for proofs drawn from culture on a large scale. 

 I am happy to be able to give them. 



From a field in Champagne, cultivated for the first time with 

 71,111 pounds of manure to the acre, 19 bushels of wheat were ob- 

 tained, while by using the complete fertilizer the return was raised 

 to 47 bushels ; from an acre of silicious earth in the department 

 of the Aisne, with 36,555.05 pounds of manure, 11.44 bushels of 

 wheat were obtained ; with chemical manure, 40.44 bushels ; the same 

 earth without any manure produced 3.66 bushels ; lastly, in the de- 

 partment of the Drome, on a pebbly hill broken up for the purpose, 

 the earth without manure yielded 4.33 bushels the acre ; with 

 34,666.06 pounds of manure it gave 11.44 bushels, and with the 

 complete fertilizer the return was 43.11 bushels. 



Monsieur Payen, in the department of the Aisne, Monsieur de 

 Matharel, in the department of the Oise, and Monsieur le Chevalier 

 Musra, in Italy, have obtained like results. 



Upon land chosen from among the poorest, where large quantities 

 *>f manure have produced 11.44 to 14.22 bushels, the complete fertili- 

 ser has determined a return of from 36 to 43 bushels the acre. 



Thus, gentlemen, a few experiments have been sufficient to define 

 the functions of all the agents of fertility that the soil should con- 

 tain or which we should furnish it by fertilizers. 



A priori, one would think that a chemical analysis which has been 

 pushed so far in our day, and whose methods have acquired at the 

 same time so much delicacy and certainty, ought at least to give us 

 a means of estimating with certainty the richness of the soil, and so 

 guiding us in the choice of the manure best suited to its nature. 

 There is, none, however, and I defy the most skillful chemist to say 

 in advance what will be the return from earth submitted to him, and 

 what manures are most appropriate. 



A few words will explain the reason why chemistry is powerless to 

 furnish us with these indications : you must recall the distinctions we 



