326 TALKS ON MANURES. 



the purchaser may be quite sure that the price is reasonable. If 

 the selling price is but $2 to $3 per ton more than the estimated 

 value, it may still be a fair price, but if the cost per ton is $5 or 

 more over the estimated value, it would be well to look further. 

 3d, Comparisons of the estimated values, and selling prices of a 

 number of fertilizers will generally indicate fairly which is the 

 best for the money. But the * estimated value ' is not to be too 

 literally construed, for analysis cannot always decide accurately 

 what is the form of nitrogen, etc., while the mechanical condition 

 of a fertilizer is an item whose influence cannot always be rightly 

 expressed or appreciated. 



" The Agricultural value of a fertilizer is measured by the benefit 

 received from its use, and depends upon its fertilizing effect, or 

 crop-producing power. As a broad general rule it is true that 

 Peruvian guano, superphosphates, fish-scraps, dried blood, potash 

 salts, plaster, etc., have a high agricultural value which is related 

 to their trade-value, and to a degree determines the latter value. 

 But the rule has many exceptions, and in particular instances the 

 trade- value cannot always be expected to fix or even to indicate 

 the agricultural value. Fertilizing effect depends largely upon soil, 

 crop, and weather, and as these vary from place to place, and from 

 year to year, it cannot be foretold or estimated except by the 

 results of past experience, and then only in a general and probable 

 manner." 



"It will be seen," said the Doctor, " that Prof. Johnson places 

 a higher value on potash now than he did 20 years ago. He re- 

 tains the same figures for soluble phosphoric acid, and makes a very 

 just and proper discrimination between the different values of dif- 

 ferent forms of nitrogen and phosphoric acid." 



"The prices," said I, "are full as high as farmers can afford to 

 pay. But there is not much probability that we shall see them 

 permanently reduced. The tendency is in the other direction. In 

 a public address Mr. J. B. Lawes has recently remarked: 'A 

 future generation of British farmers will doubtless hear with some 

 surprise that, at the close of the manure season of 1876, there were 

 40,000 tons of nitrate of soda in our docks, which could not find 

 purchasers, although the price did not exceed 12 or 13 per ton.' " 



" He evidently thinks," said the Doctor, " that available nitro- 

 gen is cheaper now than it will be in years to come." 



"Nitrate of soda," said I, "at the prices named, is only 2| to 2f 

 cents per lb., and the nitrogen it contains would cost less than 18 

 cents per lb., instead of 24 cents, as given by Prof. Johnson." 



"No. 1 Peruvian Guano, * guaranteed,' is now sold," said the 



