Page:Popular Science Monthly Volume 64.djvu/341

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seat of life; the brain first receives impressions; the nerves; the anatomy of the eye; its humors; the function of vision; vision is the result of radiation; vision is not completed in the eye but in the brain; matter is infinitely divisible; as many divisions can be made in a grain of millet as in the diameter of the world; theory of color; conditions of vision; time is required for the propagation of light; double images; radiations from the object and from the eye; perception; the Milky Way is a multitude of small stars clustered; shooting stars are probably bodies of small magnitudes seen by (persistent vision); phases of the moon; the surface of the heavens is spherical; illusions respecting relative motion; twinkling of stars; animals pass through a train of mental processes akin to syllogistic reasoning, though they can not put it into a logical figure; they have a storehouse of mental impressions; can generalize and draw conclusions.

On Reflected Vision.—The angles of incidence and reflection are equal whether the mirror be plane or spherical; mirrors; illusions; color; refraction; by refraction great wonders may be wrought; small things may be made to seem great, distant things near.

Moral Philosophy.—Civic morality; personal morality; we must pursue our steady course, not diverted from it by the varying blasts of opinion; proof of the truth of the Christian religion; revelation is necessary; it is not enough for the reason to be convinced in this matter—the heart must be stirred. If we are made one with God and Christ, to what greater good can we aspire?

The thirteenth century is memorable by the appearance of three great men, Roger Bacon, Albertus Magnus and St. Thomas Aquinas. Albert was born in Suabia in 1193, the descendant of a celebrated and powerful family. He may be reckoned as the best product of the middle ages. He studied in Padua and Bologna, taught at Cologne and Paris (1245) and returned to Cologne. He became provincial of the Dominicans in Germany in 1254, and was Bishop of Ratisbon (in 1260) till he resigned about 1263. He was the friend of kings and popes. His great service to the church was a systematic presentation of the philosophy of Aristotle with a full accompaniment of Arab commentary. Among his contemporaries he was known as Doctor Universalis, and, in the history of the world, is especially famous for his works on physical science. Like all the learned men of his time he was supposed by the vulgar to practise magic and, as a matter of course, he sought the philosopher's stone. It was even currently believed that he paid the large debt of his bishopric of Ratisbon with transmuted gold. The flowers that he grew in the winter time, which the wondering townsfolk called magical, were in all likelihood the product of the first hot-house constructed in Europe. An edition of his works in twenty-one volumes was first published in 1651. This complete collection shows, in the first place, that he was thoroughly familiar with all the learning of the Arabs up to his own time. He was to the west what Avicenna was to the east, an encyclopedia of all knowledge. His philosophy is, of course, Aristotle's, elucidated by the schools of Arabia and Spain. His works on physical science are, in a large degree, mere reproductions of Greek treatises, but they are