Observations on South American and African Guano, 295 



solution was coloured slightly brown, seeming to show, that bed- 

 sides the formation of some oxalate of ammonia, in this instance, 

 a soluble matter also was produced, which, it may be oonjeo» 

 tured, is analogous to that which exists in the guano, impart- 

 ing colour to it. 



Before concluding, I would wish to say a few words relative 

 to the tests of guano, — the means of distinguishing between 

 the genuine and the spurious kinds. Taking into account it» 

 origin, and that deposits of it can be found only where no 

 rain falls, the inference seems now to be obvious, either, if 

 old, that it must abound in oxalate of ammonia ; or if, com- 

 paratively of little age, in lithate of ammonia ; or if not of 

 great age, it must contain a notable quantity of both these 

 substances. These salts are easily detected, and the first 

 mentioned, very readily by the microscope. 



The adulteration of the genuine kind, to which the tempter 

 tion is great, cannot be so easily detected. I fear it cannot 

 be accomplished, excepting by means of chemical analysis ; 

 and that the farmer must hold himself dependent on the inte- 

 grity of the merchant; and if he would wish to avoid the- 

 chances of imposition, he must purchase only of the merchant 

 of established name, and at the regular price. 



As guano appears to be constantly exhaling ammonia on 

 exposure to the atmosphere, to prevent loss and deterioration, 

 it cannot be, before use, too carefully excluded from the air ; 

 and on the same account, it ought not be applied as a manure, 

 whilst vegetation is inactive, but rather at the moment of its 

 coming into activity, and when in progress, according to the 

 Peruvian manner of bestowing it on the plant, rather than on 

 the soil. 



I have alluded, in the beginning of this notice, to the spirit 

 of enterprise displayed in the importation of guano. I have 

 since learnt, that, in procuring the African kind, that which I 

 have examined, no ordinary degree of this quality has been 

 exerted, accompanied by a boldness of daring, and a perse- 

 verance worthy of record. The importer, Mr Rae, informs 

 me, in a letter with which he has just favoured me, that his 

 son is the discoverer of the guano-islet or islets, for it would 

 appear that there are several of them, so remarkably situated. 



