which produces those ever more rapidly recurring changes in environment to which men must adapt themselves at their peril. As, under the stimulant of modern science, the old types fail to sustain themselves, new types have to be equally rapidly evolved, and the rise of a new governing class is always synonymous with a social revolution and a redistribution of property. The Industrial Revolution began almost precisely a century and a half ago, since when the scientific mind has continually gained in power, and, during that period, on an average of once in two generations, the environment has so far shifted that a social revolution has occurred, accompanied by the advent of a new favored class, and a readjustment of wealth. I think that a glance at American history will show this estimate to be within the truth. At the same time such rapidity of intellectual mutation is without precedent, and I should suppose that the mental exhaustion incident thereto must be very considerable. In America, in 1770, a well-defined aristocracy held control. As an effect of the Industrial Revolution upon industry and commerce, the Revolutionary War occurred, the colonial aristocracy misjudged the environment, adhered to Great Britain, were exiled, lost their property, and perished. Immediately after the American Revolution and also as a part of the Industrial Revolution, the cotton gin was invented, and the cotton gin created in the South another aristocracy, the cotton planters, who flourished until 1860. At this point the changing of the environment, caused largely by the railway, brought a pressure upon the slave-owners against which they, also failing to comprehend their situation, rebelled. They were conquered, suffered confiscation of their property, and perished. Furthermore, the rebellion of the aristocracy at the South was caused, or at all events was accompanied by, the rise of a new dominant class at the North, whose power rested upon the development of steam in transportation and industry. This is the class which has won high fortune by the acceleration of the social movement, and the consequent urban growth of the nineteenth century, and which has now for about two generations dominated in the land. If this class, like its predecessors, has in its turn mistaken its environment, a redistribution of property must occur, distressing, as previous redistributions have been, in proportion to the inflexibility of the sufferers. The last two redistributions have been painful, and, if we examine passing phenomena from this standpoint, they hardly appear to promise much that is reassuring for the future.