128 NATURAL MANURES. VI. 



The addition of kainite, or better, of acid substances, e,y., 

 free sulphuric acid or superphosphate, has been highly recom- 

 mended as a means of preserving nitrogen. Heiden" states 

 that by strewing the stalls in which cattle are kept three times 

 a. day with superphosphate at the rate of 2R). for every 100011). 

 live weight a great economy is effected in the manure, and this 

 is true whether the stalls are cleaned out frequently or the 

 dung and litter be left under the cattle for six weeks. 



From extensive experiments made by Holdefleissf, the effect 

 of covering the manure with earth was sho\vn to greatly pre- 

 serve the nitrogen, while allowing of the fermentation and 

 consequent loss of the carbonaceous matter ; superphosphate 

 and kainite, which also prevent loss of nitrogen, when applied 

 at the rate of about 2% of the manure, interfere with other 

 fermentative changes and allow the straw to remain practi- 

 cally intact. Hence they act as antiseptics rather than 

 absorbents. 



Other Organic Manures. A number of other refuse 

 matters of vegetable or more frequently animal origin are 

 used as manures, the chief being 



Guano. 



Pigeon and fowl dung. 



Fish refuse or fish guano. 



Sea- weed. 



Dried blood. 



Meat meal or meat guano. 



Bones. 



Woollen refuse, shoddy manure. 



Soot. 



Oil-cakes, and oil-seed refuse. 

 These can only be briefly dealt with here. 



Guano is the dried dung of sea birds, together with portions 

 of their feathers, bones, and the refuse of their food ; the older 

 deposits also contain the remains of seals, \valruses, &c. 

 Guano accumulates on islands or near the coasts in tropical 

 climates, the chief deposits being found in North and South 



* Bieder. Centr. 17, 154 ; J. Soc. Chem. Ind. 1888, 332. 

 t Jahresbericht iiber Agricultur-Chemie ]'.00, 117. 



