8 VOELCKER on the Value of Artificial Manures. 



a greater commercial value than guano, because under peculiarly 

 favourable circumstances it produces more beneficial results. 



Bones have been known to fail altogether on some soils, for 

 the very obvious reason, that these soils contained already a 

 more than sufficient supply of phosphates to meet all the wants 

 of the plants, or because the closeness of the soil hindered the 

 decomposition of the bone ; but surely failures of that kind do 

 not imply that bone-dust is worth nothing. A few years ago 

 we examined an artificial manure, which was sold at 8/. per ton. 

 Several testimonials from practical men expressed a very favour- 

 able opinion of its merits. However, on analysis it was found 

 to contain mere traces of ammonia and phosphoric acid, and no 

 less than 88 per cent, of carbonate of lime, with some charred 

 spent tanner's bark, and sand. It was in reality a mixture of 

 road-scrapings with some charred tan refuse, and hardly was 

 worth the carriage from London to Gloucester. Notwithstand- 

 ing its exceedingly low commercial value, its efficacy on soils 

 greatly deficient in lime was very marked. But it is evident 

 that the beneficial effects it produced under certain favourable con- 

 ditions did not entitle the manufacturer to demand the exorbitant 

 price at which this manure was actually sold. Again, let us 

 suppose the money-value of Peruvian and Saldanha-bay guano 

 were to be determined by their effects on turnips. In this case 

 Saldanha-bay guano, which is much richer in phosphates than 

 Peruvian, would produce the heavier crop, and we would arrive 

 at the absurd conclusion that Saldanha-bay guano was worth 

 more money than Peruvian. Both guanos tried upon wheat 

 would reverse the result ; for wheat is more benefited by am- 

 monia than by phosphates ; and as Peruvian guano contains 

 16 per cent, of ammonia, and Saldh ana-bay only 4 to 5 per cent., 

 we can readily explain the superior efficacy of the latter upon 

 wheat. Does not this plainly show that the commercial value of 

 guano does not necessarily depend on the effects which it is 

 capable of producing on certain crops ? Indeed, for turnips the 

 cheap Saldanha-bay guano is more valuable than the more ex- 

 pensive Peruvian. 



Another instance brought lately under our notice may be men- 

 tioned in illustration of the necessity of distinguishing between 

 the practical effects of a manure and its commercial value. A 

 guano, for which the full price of the best Peruvian was paid, on 

 analysis was found to contain only 11 instead of 16 per cent, of 

 ammonia and 14^ per cent, of sand. Now, though it was evi- 

 dent that the commercial value of this guano was considerably re- 

 duced by the latter impurity alone, we were told by the purchaser 

 that he had obtained a better crop of wheat with this guano than 

 with any other sample he had tried in previous years, and that 

 he therefore considered it a first-rate article. 



