Frank A. Fetter,
The Principles of Economics, with Applications to Practical Problems
“ The school-room, laboratory, or college class-room could be used at midnight, it is true, but not conveniently; and as students increase, buildings must be added. The same is true of any industry. We cannot conveniently increase the business of a lumber-yard without a larger yard-space, or of a factory without a larger floor-space. But the added space may be gotten by spreading horizontally or piling up perpendicularly. A ten-story building on an acre lot represents ten acres of floor-space. Putting up higher buildings is an expansion in area by the more intensive utilization of the land. ”
