Scientific Research and Invention 137 
industry, subject to the tyranny of the law of 
“decreasing returns.” At a given stage of the sci- 
ence and art of agriculture, additional bushels of 
wheat or of any other crop could be wrested from 
the soil only with a disproportionately increased 
expenditure of labor and capital. If there were no 
changes in the methods of agriculture, foodstuffs 
and other raw materials and products of the farm 
must continuously advance in price as population 
increases and the demand for farm products grows. 
But this, which was the logic of Ricardo, Malthus 
and their followers, implies that practices and appli- 
ances remain unchanged. Under such assumptions 
the theory is correct. But economists cannot reckon 
without taking account of the scientific researchers 
and inventors who have revolutionized agriculture 
half a dozen times since the eighteenth century, 
until today scientific farming has been transformed 
almost into a manufacturing industry. 
Subsoil plowing, better fertilizers, better breeds 
of farm animals, new and improved crops, utiliza- 
tion of waste products, and, last and most important, 
improved means of transportation have increased 
manifold the area and productivity of economic 
land since Ricardo laid down his famous law of rent, 
based upon the “permanent and indestructible qual- 
ities of the soil.” 
Agricultural chemists long ago taught the farmer 
the value of soil analysis for showing what lands 
are suited to particular crops, what kinds of ferti- 
lizer to use. These chemists have found hundreds