in this excerpt form an 1896 essay, architect louis sullivan describes certain conditions typical of growing urban centers in the us. . . . continued growth of population in the great cities, consequent congestion of centers and rise in value of ground, stimulate an increase in number of stories; these, successfully piled one upon another, react on ground values . . . based on this description, which conclusion can a reader most reasonably draw about urban growth in the us at that time?