274 General History oj Europe and that this had "not as yet put forth all its branches nor produced all its fruits." "If we' could continue to live for endless centuries we mortals could never hope to reach full and complete knowledge of all the things which are to be known." 456. Bacon foresees Great Inventions. Bacon declared that if men would only study common things instead of reading the books of the ancients, science could - outdo the wonders which magicians of his day claimed to perform. He said that in time men would be able to fly, would have carriages which needed no horses to draw them and ships which would move swiftly without oars, and that bridges could be built without piers to support them. All this and much more has come true, but inventors and modern scientists owe but little to the books of the Greeks and Romans, which the scholastic philosophers and the Humanists relied upon. Although the Greek philosophers devoted consider- able attention to natural science, they were not much inclined to make long and careful experiments or to invent anything like the microscope or telescope to help them. Aristotle thought that the sun and all the stars revolved about the earth and that the heavenly bodies were perfect and unchangeable. He believed that heavy bodies fell faster than light ones and that all earthly things were made of the four elements earth, air, water, and fire. The Greeks and Romans knew nothing of the compass, or gunpowder, or the printing press, or the uses to which steam can be put. Indeed, they had scarcely anything that we should call a machine. 457. Discoveries of the Thirteenth Century. The thirteenth century witnessed certain absolutely new achievements in the history of mankind. The compass began to be utilized in a way to encourage bolder and bolder ventures out upon the ocean. The lens was discovered, and before the end of the century spectacles are mentioned. The lens made possible the later telescope, microscope, spectroscope, and camera, upon which so much of our modern science depends. The Arabic numerals began to take the place of the awkward Roman system of using letters. One can- not well divide XL VIII by VIII, but he can easily divide 48 by 8.
