Scientific Research and Invention 139 
highest power to absorb nutrients from the soil, Dr. 
Willcox says, may permit a maximum density of pop- 
ulation of ninety-six thousand people per square 
mile! 
What has been said of farming is also true of 
other basic industries. The wastes of our forest 
areas have become and will become increasingly the 
sources of foodstuffs, of specialized building mate- 
vials and of chemicals of great value. If research 
and invention should cease, the Malthusian law of 
population might begin to. operate rigorously and 
property grow apace. But we are only just begin- 
ning to scratch at the surface of the earth for the 
material conveniences and sources of power which 
can be made to minister to our needs and comforts. 
Our continued progress in well-being rests abso- 
lutely upon the ability of the chemists, physicists 
and engineers to- extract further utilities from the 
earth faster than the ever-growing population can 
consume them. 
But the rate at which they have accelerated this 
process in recent years readily accounts for the 
increased real income of the nation, which, with 
its prospects of still greater income, have warranted 
the higher plateau of securities by which the nation’s 
industries and economies are valued. The prospects 
of still greater income need emphasizing. The diffi- 
culty in most cases has been that the securities 
affected by inventions and rapid growth have often 
been sold at high prices after and not before the 
greatest ratio of growth took place. It is future