tical nature led them to the execution of great engineering works, their roads, aqueducts and baths still remaining for our admiration to-day. After the fall of the Romans succeeds the long night of the dark ages, learning being kept alive only by the Saracens, and the achievements of the Greeks being so far forgotten as to require to be discovered anew. Finally came the fall of Constantinople with the dispersal in Europe of many Greek scholars, the Renaissance, and the revival of learning. Conditions were then ripe for the prosecution of all sorts of intellectual pursuits, and we find the study of nature for itself taking on a development never before dreamed of. To these the church, in many cases, did not offer a welcome. Accustomed, during the middle ages, to the supreme domination over men's minds, she did not look with favor on a movement destined to set them free from all bonds except the truth. Copernicus died too soon to come into conflict with the power of the church, but upon his follower Galileo she wreaked her vengeance, and Giordano Bruno she burned at the stake. Nevertheless, the powerful genius of Galileo gave rise to so many and so important discoveries as to constitute him the father of modern science. Not satisfied with the introspective methods of the Greeks, who often contented themselves with considering how nature ought to work, he developed the modern method of the direct appeal to nature, by means of experiment finding out how she actually did work. When in the presence of the scoffing schoolmen he dropped the heavy and the light weight from the top of the tower of Pisa, and found them both to reach the ground together, he sounded the death-knell of the old and outworn Aristotelian philosophy.
It is not my intention here to consider the history of science, and its development from the small beginnings of the cinquecento through its glorious burst in the eighteenth century to full fruition in the nineteenth. Let us briefly recapitulate some of the changes which the works of science have made in the face of the earth, and of mankind inhabiting it. First and most important is the production of power, by which man's energies are inconceivably multiplied. The discovery of coal at just the right time to be utilized in the invention of the steam engine enabled man to command hitherto undreamed of forces, making the constructions and manufactures of the ancients seem like child's play. The raising of cotton, made practical by the invention of the cotton gin, largely transformed the clothing of the world, while the development of the iron and steel industry revolutionized methods of construction. With the command of power in centralized units came the development of the industrial system, and the tendency to crowd together into cities, leading to so many scientific problems yet unsolved. With the tremendous increase in the wants of humanity brought about by the increased power to supply them, the supply of natural energy in the form of coal, which at first seemed inexhaustible,
