162 IMPORTANCE AND VALUE 



gain assistance by proposing the question, How 

 could the ingredients of the manure, whose value is 

 to be determined, have been procured most cheaply 

 in another way ? Hence I have looked around for 

 such materials as are met with in abundant quan- 

 tity upon the earth, and by means of which one or 

 another of the manuring constituents could be fur- 

 nished at the lowest possible cost. From the mar- 

 ket value of these materials, the price to be placed 

 upon the individual ingredients was then ascertained ; 

 but this, in many cases, must again be modified, 

 for if it is taken as the groundwork for calculating 

 the worth of those manures that are actually met 

 with in commerce, and possess a fixed market value, 

 a disproportionate price, ^ differing widely from the 

 assumed commercial value, is established. A per- 

 fect unison between the actual ana the theoretical 

 price cannot therefore be always obtained by this 

 mode of computation; nevertheless, I maintain that 

 the differences which will occur in the calculations 

 to be presently brought forward, by way of illustra- 

 tion, are of such a character, that the theoretical 

 price, obtained by the method of reckoning here 

 adopted, is entitled to be regarded as more accurate 

 than that actually exhibited in the present state of 

 trade. 



It is impossible to specify the reasons in detail 

 which have induced me to increase the price of one 

 substance and to reduce that of others, because the 

 entire valuation depends in general more upon a re- 



