294 AMMONIA AXD NITRIC ACID. 



the fact that horn, claws, blood, bones, urine, the sohd 

 excrements of animals and men, exerted a favom'able 

 influence ; while woody substances, sawdust and similar 

 materials, had no effect, or as good as none. If in the one 

 case the presence of nitrogen was the reason of activity, 

 so in the other case the want of nitrogen caused the want 

 of activity ; in short, by the operation of nitrogen all 

 facts seemed to be harmonised and explained. 



If the nitrogenous manures depended for their activity 

 upon the nitrogen which they contained, it followed 

 necessarily that all of them could not possess the same 

 value for the farmer, because they did not all contain the 

 same amount of nitrogen ; those which had more of this 

 substance were manifestly more valuable than those which 

 had less. The amount of nitrogen was easily determined 

 by chemical analysis ; hence arose the idea to draw up 

 for the benefit of farmers a hst of manures with a figure 

 attached to each sho^\dng its relative value ; those which 

 were most abundant in nitrogen were considered the 

 most valuable, and stood liighest in the list. 



In this valuation no importance was attached to the 

 form which nitrogen assumed in the various manures, and 

 just as httle to the substances which were present along 

 with the nitrogenous compound. Li this hst it was quite 

 immaterial whether the nitrogenous combination was m 

 the form of gelatine, horn, or albumen ; or whether these 

 substances were or were not accompanied by earthy or 

 alkahne phosphates. Dried blood, claws, horn shavings, 

 woollen rags, bones, rape-cake meal, all figured in one and 

 the same hst. 



As no definite combination was understood by the 

 word ' nitrogen,' it was impossible to prove that the 

 operation of nitrogenous manures bore any proportion to 

 the amount of nitrogen which they contained. 



