EXPEKIMENTS OF LAWES AND GILBERT. 283 



enhance the fertility of a field, but that the crop of corn 

 and straw stood rather in proportion to the supply of 

 ammonia. In fact, that increased crops could be ob- 

 tained by salts of ammonia alone, inasmuch as nitro- 

 genous manures were peculiarly adapted -for the culti- 

 vation of wheat. 



The experiments of Messrs. Lawes and Gilbert are 

 very far, indeed, from proving the conclusions which 

 they wish to draw ; they establish rather the fact that 

 f these gentlemen have not the slightest notion of what 

 is meant by argument or proof. 



They did not attempt to discover whether salts of 

 ammonia alone could produce from one portion of a 

 field continuous larger crops than were yielded by an 

 unmanured portion of the same field. 



Neither did they attempt to discover what crops 

 would be yielded by an equal plot of ground by ma- 

 nuring with superphosphate and potash salts during 

 a series of years. But in the first year they supplied 

 a plot of ground for a whole series of years with the 

 constituents of corn and straw, phosphoric acid and 

 silicate of potash (560 Ibs. of bone-earth rendered solu- 

 ble by sulphuric acid, and 220 Ibs. of silicate of potash), 

 and manured it, in the following years, with salts of 

 ammonia only, and they would have us to believe that 

 the increased crops obtained under these circumstances 

 were due to the operation of salts of ammonia alone ! 



The imperfect nature of the experiments made by 

 Messrs. Lawes and Gilbert will appear, perhaps, more 

 striking, if the question which they pretend to solve 

 is stated in another form. "We will assume that the 

 point to be proved was, that the high additional crops, 

 yielded by a wheat field manured with guano, were 

 due to the operation of the salts of ammonia in the 

 guano, and that its other constituents had no share in 

 the work. If the guano had been lixiviated with water, 

 and two portions of a field had been manured, the one 

 with guano, the other with the soluble constituents of 

 an equal quantity of guano, only two cases could occur ; 

 the crop of both plots would be either equal or unequal. 



