RULES AND MEASURES. 225 



cotton states a great deal of cottonseed is exchanged for 

 cottonseed meal. The basis of exchange must rest on the 

 commercial value of the feeding and fertilizing elements 

 contained in each. Since both of these materials are used 

 in great quantities as carriers of commercial plant food, 

 the fertilizing value primarily governs the selling prices, 

 and also becomes the basis of exchange of seed for meal 

 at the oil mill. 



Determining Basis of Exchange. 



One ton cottonseed contains : 



Ammonia, 75 pounds at 16 cents, $12.00 



Phosphoric acid, 26 pounds at 5 cents, 1.30 



Potash, 24 pounds at 5.4 cents, 1.30 



Fertilizing value, $14.60 



One ton cottonseed meal contains : 



Ammonia, 170 pounds at 16 cents, $27.20 



Phosphoric acid, 56 pounds at 5 cents, 2.80 



Potash, 36 pounds at 5.4 cents, 1.94 



Fertilizing value, $31.94 

 31.94 -^ 14.60 = 2.19 



Which means that, at the prices assumed, cottonseed meal con- 

 tains 2.19 times as much fertilizing materials as cottonseed. 



Cost of transfer. The seed must be hauled to the oil 

 mill and the meal must be hauled back to the farm. From 

 the standpoint of fertilizing values an exchange of 2,000 

 pounds of .seed for (2,000 -5- 2.19 = 913) pounds of meal 

 would be .equitable. The farmer should receive, then, an 

 additional quantity of meal sufficient to cover the expense 

 and trouble of hauling or he will lose by the transaction. 



826. A farmer -exchanges one ton of seed for meal 

 at the oil mill. He finds it costs him $2 for the time and 

 labor. How many pounds of meal will be required in ex- 

 change for the ton of seed after allowing for the expense 

 of the trip ? 



