Composition and Value of Guano. 197 



To obviate this defect, and to place in a clear light the differ- 

 ences which exist between the different varieties — to contrast the 

 money value of the specimens — and, having decided upon the 

 constituents to which their manurial efficacy is to be ascribed, to 

 speculate upon the possible substitutes for guano on the score of 

 economy, or in the event of an ultimate failure of its supply — such 

 are the objects of the present paper. 



It is taken for granted that no one vi^ho will take the trouble of 

 reading papers of a scientific character in reference to agriculture 

 needs to be furnished with arguments to prove that guano acts as 

 a manure because it contains something or other that is favourable 

 to the growth of plants, that is to say, that there is no talismanic 

 or mysterious principle about it which would elude inquiry or 

 defy imitation, but that it is perfectly practicable to ascertain 

 what the constituent or constituents are which make it a fertilizer; 

 and that, having so ascertained its active ingredients, di fac simile 

 of the substance might be prepared by a combinati(m of them 

 from other sources ; and that, whatever these sources might be, 

 the compound so prepared would have all the properties and 

 efficacy of the guano which it was intended to imitate.* 



Guano then owes its efficacy as a fertilizer to some one or more 

 definite ingredients. The question is. Do we know what the 

 active constituents of guano are? and is its composition for the 

 practical purposes of agriculture capable of being regarded in a 

 simple light, and of being made the subject of distinct calculation? 

 It is hoped that these queries may very readily be answered in 

 the affirmative. 



For an instant let the reader give his attention to the elaborate 

 analyses of guano before alluded to. He will find that mention is 

 made of the urate, oxalate, humate, &c., of ammonia ; these are 

 what chemists call " organic salts :" then, again, of the phosphate, 

 carbonate, and muriate of the same alkali. He will also observe 

 that guano contains sulphates, carbonates, phosphates, and mu- 

 riates of lime, magnesia, potash, and soda; and lastly, organic 

 matters containing^ nitrog-en. Now what does all this amount to? 

 Is it meant that every one of these compounds has its distinct and 

 individual share in the action of guano as manure ; that the oxalate 

 of ammonia will have a different effect, and consequently a different 

 value, to the carbonate ; that it will be of material importance that 

 the phosphate of lime and the phosphate of magnesia should be 

 separately considered? Surely not. It was before observed, that 

 the analyses in question are of a scientific rather than a practical 

 tendency, and that they were not made with a view to agricultural 



* This is not literally true. Uric acid is only to be obtained from one or two 

 sources, such as the solid urine of serpents or the dung of sea-fowl, which latter is in 

 fact guano. Guano is therefore a manure sui generis, and it is impossible to produce a 

 perfect imitation of it. 



