CONTENTS. xiii 



CHAPTER XVI. 



ASTRONOMY OF THE NINETEENTH CENTURY. 



BODE'S Law, 417 Piazzi, 418 The Asteroids, 418 John Couch Adams, 424 

 Le Verrier, 424 Sir John Herschel, 428 Edward Troughton, 432 Astronomical 

 Telescopes, 433 Fraunhofer, 436 Distance of Stars, 437 Pendulum Experi- 

 ments, 437 Observatories, 440. 



CHAPTER XVII. 



PHYSICS OF THE NINETEENTH CENTURY LIGHT. 



Page 442 



* DR. Thomas Young, 442 Interference of Light, /|/|4 Physiological Optics, 445 

 The Undulatory Theory, 447 Colours of Thin Films, 449 Stephen Louis 

 Malus, 451 Auguste Jean Fresnef7*454 Refraction and Reflection Explained, 

 458 Double Refraction, 461 Polarization, 462 Interference Explained, 463 

 Transverse Vibrations, 468 Polarization Explained, 469 Interference and Polari- 

 zation, 473 Francois Arago, 474 Conical Refraction, 475. 



CHAPTER XVIII. 



PHYSICS OF THE NINETEENTH CENTURY SPECTROSCOPY. 



Page 476 



WILLIAM Hyde Wollaston, 477 Fraunhofer, 480 Qojoured Flames, 481 

 Absorption Bands, 483 Kirchhoff, 484 The Spectroscope in Chemical Analysis, 

 4^5 Celestial Chemistry, 493 Dr. Huggins, 496 Photographic Spectra, 498 

 Constitution of the Sun, 499 Theory of Spectra, 502. 



CHAPTER XIX. 



PHYSICS OF THE NINETEENTH CENTURY (continued) OPTICS, RADIATION, 

 HEAT, AND SOUND. 



Pa%e 505 



FIZEAU, 505 Leslie, 507 Melloni, 508 Dr. Tyndall, 510 Solar Radiation, 

 512 Dr. Draper, 514 Microscopes and Telescopes, 514 Sir David Brewster, 

 517 Crookes' Experiments, 518 Dr. J. R. Mayer, 524 James Prescott Joule, 

 524 The Mechanical Equivalent of Heat, 527 Gay-Lussac, 530 M. Regnault, 

 530 Leidenfrost, 532 Boutigny, 532 Sound, 533 Sauveur, 534 Colladon and 

 Sturm, 535 Dr. Brook Taylor, 537 E. F. Chaldni, 537 Cragniard de la Tour, 

 539 M. Felix Savart, 540 Hermann Louis Helmholtz, 542 Graham Bell, 546 

 Edison, 546. 



