MICHIGAN ACADEMY OF SCIENCE. 
45 
These experiments have, however, served a purpose, in that they have 
taught us the direction in which soil investigations of the future must 
lead. The introduction of a chemical substance into the soil changes the 
condition, not only in respect to the material added but to those already 
present. It also may and probably does alfect the physical and biologi- 
cal condition as well as the chemical. 
The method practiced by some experimenters of analyzing a soil 
sample representing the first eight or ten inches and from the results 
estimating the number of bushels of grain or the number of years that 
the soil will produce a certain sized grain crop before it becomes ex- 
hausted is unscientific and unsound. The time is now ripe when we 
should attack these problems in a truly scientific way. 
While of course greater productive capacity is the ultimate aim of the 
soil investigator he should seek to find out and understand the changes 
taking place in the soil that accompany greater production. 
Michigan Agricultural College, East Lansing, Midi., April, 1911. 
