258 GUANO. 



alkaline earths may have a certain connection "s\dth the pre- 

 sence of the soluble nitrogenous compoimds (albumen and 

 casein), or of the insoluble (gluten or vegetable fibrine). 

 Of course, the quantity of potash and soda present would 

 have to be taken into account in an investigation of the 

 kind. The fertihsing action of guano is generally attri- 

 buted to the ammonia in it, and to the other ingredients 

 rich in nitrogen ; but accurate experiments made to elu- 

 cidate this point, by the General Committee of the Agri- 

 cultural Society of Bavaria, which we shall hereafter have 

 occasion to mention, have shown that whilst the use of 

 guano was found, in many cases, to increase very con- 

 siderably the produce of corn and straw of a field, the 

 apphcation of an ammoniacal salt containing an amount 

 of nitrogen corresponding to that in the guano produced 

 no perceptible effect on the crop of the same cereal, 

 grown in the same year, upon another plot of the field, 

 when compared with the produce of a third unmanured 

 plot of the same field. 



Though the part which the ammonia in the guano 

 plays, in many cases, in increasing the produce, cannot 

 be questioned ; yet it is equally certain, on the other 

 hand, that in many other instances the fertilismg action 

 of guano must be attributed principally to its other con- 

 stituents. 



If the ash of guano is compared with calcined bones, 

 or bone-earth, it is foimd that the difference between the 

 two is not very great; yet an amount of bone-earth 

 containing the same proportion of earthy phosphate as in 

 guano, or even two to four times that quantity, has not 

 the same action as the latter manure. Even a mixture of 

 bone-earth with ammoniacal salts in sufficient proportion 

 to make the amount of nitrogen and phosphoric acid 

 equal to that contained in the guano, though more 



