Farmyard Manure. 127 



All animal smell was instantly removed in each of the three 

 boxes, but there remained a faint but perceptible smell of am- 

 monia in the first box, sprinkled with M'Dougall's powder. In 

 the second box, sprinkled with gas-lime, the smell of ammonia 

 was still more distinct ; and in the third box, sprinkled with 

 slaked lime, the smell of ammonia was most marked. 



It thus appears from these experiments that whilst all three 

 powders removed instantly the peculiar animal smell which pre- 

 vails in stables, none possessed the power of fixing free ammonia. 



In the experiment with M'Dougall's powder the smell of 

 ammonia was masked by the tarry products contained in this 

 powder to an extent which rendered it difficult to an inexpe- 

 rienced person to recognise by the smell alone the presence of 

 free ammonia. On the other hand, the smell of ammonia in the 

 third loose box was decidedly stronger after sprinkling the floor 

 with slaked lime and tar than before the experiment. As 

 M'Dougall's powder contains only little caustic lime, the pre- 

 pared lime a good deal more, and the slaked lime most caustic 

 lime, it is evident that the differences in this respect are mainly 

 due to the relative quantities of caustic lime present in the three 

 experimental powders. The experiment with slaked lime, more- 

 over, shows that the excrementitious matters on the floor of 

 stables contain ammoniacal salts, from which ammonia is libe- 

 rated by caustic lime. 



%icl Set of Experiments. 



Some of M'DougaH's powder was next added to fresh farm- 

 yard manure. The peculiar animal smell of the latter was 

 rapidly removed, but ammonia — it is true, in small quantities, but 

 still in a perceptible degree — lil)erated at the same time. 



An equal portion of fresh farmyard manure was treated with 

 prepared gas-lime, and a third portion of fresh dung with slaked 

 lime and gas-tar. 



The two last-named powders rapidly destroyed the disagree- 

 able animal smell of the dung, and, like M'Dougall's powder, 

 liberated some ammonia. 



Similar experiments were tried with three equal portions of 

 well rotten dung with similar results. In each case ammonia 

 was given off in small quantities, especially in the experiment in 

 which slaked lime was added to rotten dung. 



In order to leave no doubt on the fact brought out by our ex- 

 periments on fresh and rotten dung, namely, that M'Dougall's 

 powder, instead of fixing ammonia, actually liberated ammonia 

 from its combinations, the following experiments were made: — 



A portion of rotten dung was put into a wide-mouthed 

 bottle, in the neck of which a moistened red litmus paper was 



