On Guano. 



309 



substance^ therefore, the guano is no less variable in composition 

 than in regard to its other constituents * 



7. When cold water is poured upon guano a large portion of 

 soluble matter is taken up, consisting chiefly of common salt and 

 of various salts of ammonia, with a very little of the urate of soda, 

 lime, and magnesia. After careful washing with water and dry- 

 ing at 150°, one portion left 40 and another 35 per cent, of inso- 

 luble residue, consisting of phosphate and oxalate of lime with 

 some urate and other animal matters. It is these soluble salts 

 which act most immediately and most powerfully when the guano 

 is applied to the growing crop. The earthy constituents, though 

 of great importance to sthe ultimate growth and health of the 

 plants begin to manifest their influence at a later period. 



8. I have not thought it necessary to determine with accuracy 

 the relative proportions of the oxalic and carbonic acids, or of the 

 several salts of ammonia, in a substance so variable in its consti- 

 tution. In the only specimen in which I sought for it I detected 

 no sensible quantity of potash. It is true that Fourcroy and 

 Vauquelin found 5| per cent, of sulphate of potash, but this can 

 only be considered as accidentally present in the specimen they 

 examined, since it is not easy to understand how potash should be 

 more abundant than soda in the excrements of sea-fowl, living 

 almost entirely upon the fish of the Pacific Ocean. 



9. Finally, the variable constitution of the guano brought to 

 this country, and now offered for sale in England, will appear by 

 the following general results of the analysis of two small portions 

 taken at random from a box containing about 20 pounds' weight. 

 The first contained 8 per cent, and the second ouly 1-i- per cent, 

 of sand. 



1- _ Percent. _ 2. Per Cent. 



Water, salts of ammonia, and or- Ammonia . . » . 7*0 



ganic matter expelled by a red Uric acid . . . ,0-8 



heat . , . . .23*5 Water and carbonic and oxalic 

 Sulphate of soda . . ,1-8 acids, &c. expelled by a red heat 51*5 

 Common salt with a little phosphate Common salt with a little sulphate 



of soda . . . , 30*3 and phosphate of soda . .11*4 

 Phosphate of lime with a little phos- Phosphate of lime, &c. . . 29-3 



phate of magnesia and carbonate 



of lime]- . . , .44-4 



100 100 



* Boussingault, after describing the astonishingly fertilising action of the 

 guano on the plains of Peru (Annales de Chun, et de Phys., Ixv. p. 319), 

 says that it consists of urate, oxalate, phosphate, and carbonate of ammonia 

 and some earthy mils. This distinguished philosopher, to whom modern 

 agriculture owes so much, inclines to the hypothesis that the fertility of the 

 soil can be increased only by the addition of substances containing nitrogen " 

 (ibid. Ixvii. p. 16), and therefore pays less regard to the earthy matters which 

 may be added to the soil. We are indebted to Sprengel for illustrating the 

 important influence of inorganic substances in nourishing and promoting 

 the growth of all living vegetables. 



t The results above given indicate the proportions of the alkaline and 



