CONTENTS. 



CHAPTER XIX. 



SCIENCE OF THE SEVENTEENTH CENTURY (CONTINUED). 



PAGB 



Transits of Mercury and Venus Kepler foretells their occurrence 

 1631, 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 . . . . . . . .153 



CHAPTER XX. 



SCIENCE OF THE SEVENTEENTH CENTURY (CONTINUED). 



Newton's Discovery of the Dispersion of Light Traces the 

 amount of Refraction of each of the Coloured Rays Makes a 

 Rotating Disc turning the colours of the Spectrum into White 

 Light Reason why all Light passing through glass is not 

 Coloured Mr. Chester More Hall discovers the Difference of 

 Dispersive Power in Flint and Crown Glass Newton's Papers 

 destroyed by his pet dog Last years of Newton's life . .161 



CHAPTER XXI. 



SCIENCE OF THE SEVENTEENTH CENTU, RY (CONTINUED). 



Roemer measures the Velocity of Light Newton's Corpuscular 

 Theory of Light Undulatoryor Wave Theory proposed by 

 Huyghens Invention of Cycloidal Pendulums by Huyghens 

 Discovery of Saturn's Ring Sound caused by Vibration of 

 Air Light by Vibration of Ether Reasons why we see 

 Light Reflection of Waves of Light Cause of Colour Re- 

 fraction explained by the Undulatory Theory Mr. Tyler's 

 Illustration of Refraction Double Refraction explained by 

 Huyghens Polarization of Light not understood till the 

 nineteenth century . . . . . . . .172 



