adding the latter together, we obtain the total
estimated value per ton.

"The uses of the 'Valuation' are, 1st, to show whether a given lot or
brand of fertilizer is worth as a commodity of trade what it costs. If
the selling price is no higher than the estimated value, the purchaser
may he 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. 2d, 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 retains the same
figures for soluble phosphoric acid, and makes a very just and proper
discrimination between the different values of different 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