In the same way our moral progress can only be measured by the obstacles we meet and overcome.
Apparently some people are ignorant, and others have forgotten, that we have no sense that is capable of discriminating between high and low speed, or even between motion and rest, except by noting the usual accompaniments of motion, such as the apparent movement of surrounding objects, the resistance of the atmosphere, or the jolting due to obstacles in the path. If our surroundings move with us and the motion is smooth, our methods of detecting it fail. Thus, we can not feel the great velocity with which the earth is moving through space. In like manner, a train on a rough road seems to be going faster at forty miles an hour than one on a smooth road at sixty. The sensations of high-speed travel depend largely, therefore, on the conditions of that travel.
