FIELD EXPERIMENTS IN AGRICULTURE. 499 



directly applicable to practice. It is not to be wondered at, then, that 

 in a time when agricultural experimentation is attracting attention as 

 never before, field experiments should be multiplied on every hand, and 

 that the public should regard the making of them as one of the chief 

 ends, if not the chief end, of experiment stations and experimental 

 farms. Both in Europe and America a vast deal of time and money 

 has been devoted to their execution, and not only have organizations 

 undertaken them, but private farmers have been urged to experiment 

 on their own farms, both with a view to obtaining a better knowledge 

 of the needs and capacities of their soils, and in the hope of advanc- 

 ing the science of agriculture. 



The literature of the subject is voluminous, particularly in rela- 

 tion to the use of manures and fertilizers, and it might be expected 

 that by this time our knowledge of these matters would be tolerably 

 complete. 



When, however, we come to look for the results of all this work, 

 we find them surprisingly meager in comparison with the expenditure 

 of time and labor which they have cost. That many valuable results 

 have been reached goes without saying ; but relatively their number 

 is small, while the number of uncertainties and contradictions is re- 

 markably great. The weakest portion of agricultural chemistry is 

 that relating to fertilizers and manures ; that is, precisely that part 

 which we should expect to find well developed. 



This state of affairs could not fail to impress thoughtful students 

 of agricultural science, and cause them to seek out the reason why a 

 method, which is apparently based upon a correct principle, and which 

 has been executed with so much labor and care, has yielded, on the 

 whole, such unsatisfactory returns. 



Quite recently two German investigators. Professor Paul Wagner 

 in Darmstadt, and Professor G. Drechsler in Gottingen, have given 

 especial attention to this question, and have reached some interesting 

 and important results, a brief account of which may not be uninstruct- 

 ive at a time when such general attention is being given to agricult- 

 ural experimentation. These two experimenters have worked quite 

 independently of each other, and their substantial agreement is strong 

 evidence of the correctness of their conclusions. 



We have said that the fundamental idea of the field experiment 

 is essentially scientific ; but, while this is true, a more critical examina- 

 tion shows that the way in which this idea has been carried into exe- 

 cution has been far from scientific. The scientific method of experi- 

 ment requires two things : 1. All the conditions of the experiment 

 must be identical, with the exception of the one whose action is to be 

 tested, and that must vary to a known extent. 2. The limits of 

 error of the methods of weighing, measuring, etc., used, must be 

 known, to the end that we may know whether any difference which 

 may be observed is accidental or significant. 



