VALUE OF ARTIFICIAL MANURES. 41 



incur the expense of an analysis, for the composition of genuine 

 Peruvian guano varies so inconsiderably, that a written guarantee 

 of a dealer, stating to furnish Peruvian guano first quality as im- 

 ported by Messrs. Gibbs, affords quite a sufficient safeguard. 

 Unless a dealer is willing to give such a general guarantee, I 

 would advise to have no transaction with him. 



There are men who guarantee Peruvian guano as imported 

 by Gibbs, but sell you an inferior article, and yet give you 

 no ground to lodge an action for damages. The fact is, 

 every year cargoes of guano, damaged by .sea-water, are im- 

 ported by Messrs. Gibbs, and sold by auction as D. or D. D. 

 guano, i. e. damaged or double damaged. A party, therefore, 

 who merely guarantees Peruvian guano as imported by Gibbs 

 may sell you a damaged guano, and it is necessary, therefore, 

 that you should get a written guarantee, in which the guano is 

 warranted genuine Peruvian jirst quality, as imported by Messrs. 

 Gibbs. 



Such a general guarantee, however, is of no use whatever in 

 buying superphosphate of lime, for there is no standard whereby 

 the genuineness of superphosphate can be tested. The fact is 

 superphosphate can be manufactured at any price from 47. to 

 121. and upwards. The manufacturer, by meeting the tastes of 

 his customers and the prices they are willing to give for this 

 manure, can readily make any quality of superphosphate. If a 

 cheap article is wanted he has only to dilute a certain quantity 

 of dissolved bones with gypsum or ashes, or use coprolites for 

 dissolving in acid instead of bone-dust. 



In buying superphosphate of lime you should therefore de- 

 mand of the maker or dealer a guarantee, which will enable you 

 to ascertain whether or not the maker of this manure is making a 

 reasonable or an exorbitant profit. Such a guarantee is afforded 

 solely in an analysis, or at least in a general statement, that the 

 bulk of superphosphate shall contain a certain amount of soluble 

 and insoluble phosphate of lime and of ammonia. For these three 

 different fertilizing ingredients determine principally the agricul- 

 tural and commercial value of superphosphate of lime. 



It is well to bear in mind that it is the soluble phosphate 

 which renders superphosphate peculiarly valuable as a manure 

 for root-crops, and that this soluble phosphate is worth at least 

 three times as much as insoluble or bone phosphates. All really 

 valuable samples of superphosphate, therefore, should be rich in 

 soluble phosphate. A manufacturer who merely guarantees 

 genuine superphosphate gives in reality no guarantee whatever. 

 The following diagram gives the composition of five samples of 

 commercial superphosphates, all sold at about the same price, i.e. 

 from 6/. to 11. per ton : 



