CONTENTS. 



CHAPTER XVII. 



SCIENCE OF THE SEVENTEENTH CENTURY (CONTINUED). 



PAGE 



Malpighi first uses the Microscope to examine Living Structures 

 — He describes the Air-cells of the Lungs — Watches the Circula- 

 tion of the Blood —Observes the Malpighian Layer in the Human 

 Skin — Describes the structure of the Silkworm — Leeuwenhceck 

 discovers Animalcules — Grew and Malpighi discover the Cellular 

 Structure of Plants — The Stomates in Leaves — They study the 

 Germination of Seeds — Ray and Willughby classify and describe 

 Animals and Plants — The Friendship of these two Men . .137 



CHAPTER XVIIL 



SCIENCE OF THE SEVENTEENTH CENTURY (CONTINUED). 



1642, Birth of Newton — His Education — 1666, His three great 

 Discoveries first occur to him — Method of Fluxions and Dif- 

 ferential Calculus— First Thought of the Theory of Gravitation 

 — Failure of his Results in consequence of the Faulty Measure- 

 ment of the size of the Earth— 1682, Hears of Picart's new 

 Measurement— Works out the result correctly, and proves the 

 Theory of Gravitation — Explanation of this Theory — Establishes 

 the Law that Attraction varies inversely as the squares of the 

 distance — 1687, Publishes the 'Principia' — Some of the Pro- 

 blems dealt with in this Work 147 



CHAPTER XIX. 



SCIENCE OF THE SEVENTEENTH CENTURY (CONTINUED) 



Transits of Mercury and Venus— Kepler foretells their occurrence 

 —1 63 1, Gassendi observes a Transit of Mercury — 1639, Hor- 

 rocks foretells and observes a Transit of Venus — 1676, Halley 

 sees a Transit of Mercury, and it suggests to him a method for 

 Measuring the Distance of the Sun — 1691-1716, Halley de- 

 scribes this method to the Royal Society — Explanation of 

 Halley's method 156 



