Farmyard Manure. 15 



never found a larger amount of free ammonia than per cent. 

 This small proportion of free ammonia cannot excite surprise if 

 the conditions are taken into account under which guano is depo- 

 sited in the rainless regions from which good Peruvian guano is 

 imported into this country. The dry and hot climate of the 

 Peruvian guano islands has the effect of leaving very little free 

 ammonia in the fresh birds' excrements, and of rapidly dissi- 

 pating the moisture which they contain. With the expulsion 

 of the moisture the further decomposition of the excrements is 

 at once arrested, and the further development of ammonia 

 prevented. 



It follows from these remarks that as long as Peruvian guano 

 is kept perfectly dry it may be preserved for any length of time 

 without losing in the slightest degree in fertilising properties, 

 and also that there exists no need of resorting to chemical sub- 

 stances which are known to possess the property of fixing 

 ammonia. 



The case is different with damaged and inferior descriptions 

 of guano. These frequently contain considerable quantities of 

 volatile carbonate of ammonia ; they are therefore liable to 

 become deteriorated on long keeping, and may be improved by 

 the addition of an acid which fixes the free ammonia. Indeed, 

 all guanos which are deposited in districts occasionally visited 

 by heavy rains contain much carbonate of ammonia, a salt which 

 in inferior guanos is often seen in beautiful large crystals, and 

 which, being volatile, is gradually dissipated by keeping. 



It has been stated already that there exists no necessity for 

 fixing ammonia in farmyard manure by chemical means. But 

 I refer again to this subject on account of a statement which has 

 been widely circulated and been reported in most agricultural 

 periodicals. It has been stated, namely, by a Mr. M'Dougall, 

 the patentee of a disinfecting powder, that by the use of the 

 patent article, not only the air in stables may be kept perfectly 

 sweet and wholesome, but that also the quality of the dung is 

 improved in an astonishing degree, so much so, that in the 

 neighbourhood of Manchester fabulous prices have been paid for. 

 farmyard manure, in the preparation of which M'Dougall's 

 powder has been used, I am bound to state at once, that this 

 powder possesses, indeed, excellent disinfecting properties ; and 

 had the inventor confined his remarks to the sanitary question 

 involved in the use of his powder, no room would have been 

 left to call in question its utility as a disinfectant. But as he 

 describes, in addition to its disinfecting properties, others which 

 I have not found confirmed in my experiments on the subject, 

 I am anxious to correct any erroneous views to which some of 

 Mr. M'Dougall's statements may have given rise. It is maintained 



