FAILURE OF THE GREEK PHYSICAL PHILOSOPHY. Bacon's Remarks on the Greeks. 494 Aristotle's Account of the Rainbow. 495 BOOK II.--THE PHYSICAL SCIENCES IN ANCIENT GREECE. Plato's Timæus and Republic. 497 Hero of Alexandria. 501 BOOK III.--THE GREEK ASTRONOMY. Introduction. 503 EARLIEST STAGES OF ASTRONOMY. The Globular Form of the Earth. 505 The Heliocentric System among the Ancients. 506 The Eclipse of Thales. 508 {21} BOOK IV.--PHYSICAL SCIENCE IN THE MIDDLE AGES. General Remarks. 511 PROGRESS IN THE MIDDLE AGES. Thomas Aquinas. 512 Roger Bacon. 512 BOOK V.--FORMAL ASTRONOMY. PRELUDE TO COPERNICUS. Nicolas of Cus. 523 THE COPERNICAN THEORY. The Moon's Rotation. 524 M. Foucault's Experiments. 525 SEQUEL TO COPERNICUS. English Copernicans. 526 Giordano Bruno. 530 Did Francis Bacon reject the Copernican Doctrine? 530 Kepler persecuted. 532 The Papal Edicts against the Copernican System repealed. 534 BOOK VI.--MECHANICS. PRINCIPLES AND PROBLEMS. Significance of Analytical Mechanics. 536 Strength of Materials. 538 Roofs--Arches--Vaults. 541 BOOK VII.--PHYSICAL ASTRONOMY. PRELUDE TO NEWTON. The Ancients. 544 Jeremiah Horrox. 545 Newton's Discovery of Gravitation. 546 {22} THE PRINCIPIA. Reception of the _Principia_. 548 Is Gravitation proportional to Quantity of Matter? 549 VERIFICATION AND COMPLETION OF THE NEWTONIAN THEORY. Tables of the Moon and Planets. 550 The Discovery of Neptune. 554 The Minor Planets. 557 Anomalies in the Action of Gravitation. 560 The Earth's Density. 561 Tides. 562 Double Stars. 563 INSTRUMENTS. Clocks. 565