Note 1 — Chapter XIII · 1891. “MORE SCIENCE.”
Reading edition
The steam engines of the world now represent the work of 1,000,000,000 men, or more than double the working population of the earth, whose total population is about 1,500,000,000 inhabitants. Steam has accordingly trebled man’s working power, enabling him to economize his physical strength while attending to his intellectual development. Our race, which seems to have reached its limit of physical development, is ready to enter upon the foretold stage of psychical evolution. ↑