136 AMERICAN MANURES. 



phosphate of lirne is worth 1J cent per pound, 

 and potash 64 cents for agricultural purposes. 

 This celebrated chemist has confined his calcu- 

 lations to the amount of these materials as found 

 in Peruvian Guano. But at this time, this is too 

 limited a basis from which to estimate their 

 value, as there are other sources from which 

 these three substances can be procured ; and as 

 respects phosphoric acid and potash, more 

 cheaply than in Peruvian Guano. 



Professor Way has estimated 10J cents per 

 pound as a fair price for soluble phosphoric acid ; 

 Dr. Voelcker, of the Royal Agricultural College, 

 of England, and Dr. Stoeckhardt, the distin- 

 guished Saxon Agricultural Chemist, give it a 

 value of 12i cents per pound. These prices are 

 deduced from the prices of the best commercial 

 superphosphates. Dr. Johnson, in his essay on 

 manures, in commenting on these prices, says : 

 "This, I believe, is considerably more than it is 

 really worth, but is probably the lowest rate at 

 which it can now be purchased." This remark 

 would seem to imply an utter helplessness on 

 his part to suggest any remedy for the prices 

 demanded. We shall review these opinions re- 

 specting the value of phosphoric acid. Dr. 

 Voelcker's and Dr. Stoeckhardt's mode of fixing 

 the price of soluble phosphoric acid, from the 

 amount of this substance contained in, and the 



