104 FIBST PRINCIPLES OF AGRICULTURE. 



2. That without a true knowledge of what constitutes 

 value, many are led to purchase on the ton basis, without 

 regard to the quantity and quality of the plant-food offered. 



Guarantee. — The fact that consumers are unable to 

 determine the value of a mixture from its appearance, 

 and the opportunity thus afforded for disguising the 

 presence of poor forms of plant-food, has led in many 

 states to the enactment of laws which require that all 

 manufacturers shall publish the actual composition of 

 their products, and also state the kind of material from 

 which the constituents have been derived; or, in other 

 words, that they shall guarantee the goods to contain 

 certain amounts and forms of the three plant-food ele- 

 ments, the state exercising a chemical control of the 

 products sold. 



By this means, spurious articles are kept from the 

 market, and good manufacturers and farmers are pro- 

 tected, though it is left still to the intelligence of the 

 farmer to determine whether there is a proper relation 

 between the guarantee and selling price. 



Interpretation of Guarantees. — The statement of the 

 guarantee is sometimes confusing to purchasers, as differ- 

 ent manufacturers use methods which seem to them most 

 desirable. The following examples illustrate this point : — 



Guarantee No. 1. 



Nitrogen (equivalent to ammonia) 3-4% 



Available Phosphoric Acid (equivalent to bone phos. of 



lime) 18-22% 



Potash (equivalent to sulphate of potash) 10-12% 



Quarantee No. 2. 



Nitrogen 2.50- 3.25% 



Available Phosphoric Acid 8.00-10.00% 



Potash (actual) 5.60- 6.50% 



