THE VALUATION OF FERTILIZERS 193 



the costs of handling and grinding do not vary according to 

 the percentage of phosphate, but according to the percentage 

 of iron which occurs as metal. 



The farmer's values may be deduced from the experiments 

 which have been conducted on the use of basic slag. Some 

 of the oldest and best known of these have been conducted 

 at Cockle Park, and are described in Gilchrist's reports 

 in the Cockle Park Guide for 1918, which show that the 

 actual profits to the farmer are something like i 155. per 

 ton for each i % of phosphate. Cockle Park is, however, 

 particularly suited to basic slag, and it would be more 

 reasonable to assume that the average profit of slag in the 

 country is considerably less. One might also safely assume 

 that the cost of cartage, etc., would be somewhat as before, 

 say i 55. per ton, hence the equation V = a -f- bp, if 

 made to represent the farmer's profits from the use of basic 

 slag, would be solved by a = about minus i 55., and 

 b = about 175. On the other hand, the amount of lime 

 in basic slag would give a plus zero value of about 45. a 

 ton, reducing the value of a to minus 2is. It will be seen 

 that a compromise has been effected in the Orders between 

 the discordant points of view of the producer and the con- 

 sumer of basic slag. It would be better for the manufacturer 

 to work with a zero value much lower than that which has 

 been assigned. 



The new orders for 1919-20 do not modify the prices for 

 basic slag sufficiently to alter the deductions drawn from the 

 1918 orders. 



The Value of Superphosphate. Superphosphate 

 presents a different case to that of basic slag and sulphate of 

 ammonia. Superphosphate is not a by-product, it is a 

 specially manufactured article. It may be true that sul- 

 phuric acid might become a waste product of zinc smelting, 

 but that day is not here yet, and in any case rock phosphate 

 must be imported and paid for by the manufacturer of super- 

 phosphate. The process, moreover, is somewhat expensive, 

 hence a higher zero point should be looked for. The manu- 

 facturer of superphosphate buys his rock phosphate on a unit 

 v. 13 



