EXPERIMENT STATION. 23 



Peruvian guano, superphosphates, fish-scraps, dried blood, potash 

 salts, plaster, etc., have a high agricultural value which is related 

 to their trade-value, and to a degree determines the latter value. 

 But the rule has many exceptions, and in particular instances the 

 trade-value cannot always be expected to fix or even to indicate 

 the agricultural value. Fertilizing eflfect depends largely upon 

 soil, crop and weather, and as these vary from place to place and 

 from year to year, it cannot be foretold or estimated except by 

 the results of past experience, and then only in a general and 

 probable manner. 



For the above first-named purpose of valuation, the trade-values 

 of the fertilizing elements which are employed in the computations 

 shoiild be as exact as possible, and should be frequently corrected 

 to follow the changes of the market. 



For the second-named use of valuation, frequent changes of the 

 trade-values are disadvantageous, because two fertilizers cannot 

 be compared as to their relative money- worth, when their valua- 

 tions are estimated from, difierent data. 



Experience leads to the conclusion that the trade-values adopted 

 at the beginning of a year should be adhered to as nearly as pos- 

 sible throughout the year, notice being taken of considerable 

 changes in the market, in order that due allowance may be made 

 therefor. It should be remembered that, in an Annual Report, 

 the fluctuations in ti'ade-value that may occur within the year 

 cannot be accurately followed, and the comparisons of estimated 

 values are mostly in reti'ospect. 



The valuations for 1882 were adopted in consultation with Dr. 

 Goessmanu, Inspector of Fertilizers for Massachusetts, and Prof. 

 Cook, Director of, and Dr. Neale, Chemist to, the New Jersey 

 Agricultural Experiment Station, and have been employed by 

 these gentlemen in their official Reports for ] 882. 



