126 Physical and Chemical Limits to Population. [March 
insist upon sharing man’s food, and from their numbers and 
theii minuteness contrive to get the first share, leaving him 
the lesidue ; or they attack our food-plants in an immature 
state, and to a great extent prevent them from growing. 
Ihese beings from rats, mice, and sparrows, down to the 
Phylloxera, and even to the Fungi which occasion the potato- 
disease, the coffee-disease, the rust and smut in wheat, 
and to the microbia of splenic fever in cattle and sheep — 
aie so numerous and varied that a mere catalogue would 
exceed the space at our disposal. Fortunately nothing of 
the kind is needed. Man hitherto has been very unsuccess- 
ful in waging war with these enemies. In how few countries 
have even the larger beasts of prey been completely stamped 
out! As for the smaller pests, they — as we have already 
hinted grow with man’s growth and strengthen with his 
strength. We have — or rather had, for they have been 
stolen by some visitor— a couple of specimens of the Colo- 
lado beetle, captured in New Mexico some thirty years ago. 
In those days it was a not very- common species, one, 
amongst other Chrysomelidae, living on wild Solanaceae, and 
not inteifeiing with man’s well-being. But as cultivation 
was extended, and as potato-fields came into existence near 
the haunts of this harmless beetle, it suddenly multiplied to 
an extent heretofore unknown, selected the potato as its 
food-plant, swept the country to the Atlantic, and destroyed 
untold thousands of tons of what would otherwise have been 
human nutiiment. Such has been the career of other ver- 
min, pests, and parasites, and such it will continue, to an 
mci easing extent, unless man finds out new and improved 
means foi theii destruction. Here, then, we have what may 
be called the biological limit to population. 
The war against poverty must be waged by means of in- 
vention and discovery. He who can increase the supply of 
plant-food, or who can form human food synthetically from 
its elements, does fai more for the well-being of his fellows 
than all the oratois and agitators of the day. But scientific 
reseal ch is less exciting to the multitude than mass-meetings, 
processions, and inflammatory harangues. 
As for the “deductions” of Mr. Henry George, we hope 
that the passage which we have quoted from his work is not 
a fair aveiage specimen ; otherwise there is woe in store for 
his followeis, and for the world at large in proportion as his 
teachings meet with acceptance. 
