106 



FIRST PRINCIPLES OF AGRICULTURE. 



the actual are shown in the following tabular state- 

 ment : 



The Unit Basis or System. What is known as 

 the "unit system" of stating the amount of plant-food 

 contained in a fertilizer is sometimes employed; the 

 " unit " means one per cent on the basis of a ton, or 

 twenty pounds. For instance, a " unit " of nitrogen 

 means twenty pounds, and a dried blood guaranteed to 

 contain ten units, means that two hundred pounds of 

 nitrogen is contained in one ton. 



This system is largely used by trade journals in stat- 

 ing quotations, particularly for nitrogenous and phosphatic 

 materials. Purchasing on the " unit basis " is the true 

 method, and hence the most satisfactory of any to both 

 the producer and consumer, and should be adopted in 

 all transactions. It means that the consumer secures 

 what he pays for, and the producer is paid for exactly 

 what he delivers. 



Purchasers should insist that any material, whether 

 mixed or unmixed, should be accompanied by a guarantee. 



Commercial Values. The commercial value of raw 

 materials is fixed by trade conditions, as supply and 

 demand, usefulness in the arts or manufacture, and 



