immensely increased ease of communication has in its turn completely changed all the physical questions of human life. A voyage from Egypt to England was nearly as serious an affair in the eighteenth century as in the second; and the news communications between the two lands were not materially improved. A graduate of your University to-day can go to mid-Asia or mid-Africa with far less consciousness of performing a feat of note than would have been the case a hundred years ago with a student who visited Sicily and Andalusia. Moreover, the invention and use of machinery run by steam or electricity have worked a revolution in industry as great as the revolution in transportation; so that here again the difference between ancient and modern civilization is one not merely of degree but of kind. In many vital respects the huge modern city differs more from all preceding cities than any of these differed one from the other; and the giant factory town is of and by itself one of the most formidable problems of modern life. Steam and electricity have given the race dominion over land and water such as it never had before; and now the conquest of the air is directly impending. As books preserve thought through time, so the telegraph and the telephone transmit it through the space they annihilate, and therefore minds are swayed one by another without regard to the limitations of space and time which formerly forced each community to work in comparative isolation. It is the same with the body as with the brain. The machinery of the factory and the farm enormously multiplies bodily skill and vigor. Countless trained intelligences are at work to teach us how to avoid or counteract the effects of waste. Of course some of the agents in the modern scientific development of natural resources deal with resources of such a kind that their development means their destruction, so that exploitation on a grand scale means an intense rapidity of development purchased at the cost of a speedy exhaustion. The enormous and constantly increasing output of coal and iron necessarily means the approach of the day when our children's children, or their children's children, shall dwell in an ironless age--and, later on, in an age without coal--and will have to try to invent or develop new sources for the production of heat and use of energy. But as regards many another natural resource, scientific civilization teaches us how to preserve it through use. The best use of field and forest will leave them decade by decade, century by century, more fruitful; and we have barely begun to use the indestructible power that comes from harnessed water. The conquests of surgery, of medicine, the conquests in the entire field of hygiene and sanitation, have been literally marvellous; the advances in the past century or two have been over more ground than was covered during the entire previous history of the human race.