£Viil 
CONTENTS. 
PAGE 
FLATE 21—(Continued.) PLATE 21—(Continued.) 
3U. Hollow prism, 293 | Fig. 89. Undulation of rays, 
OL. Dulong’s apparatus for determin- « 90. Illustrating the theory of interfer- 
ing the refractive powers of ence 
gases, 293 Ot Illustrative of the explanation of 
32. The six kinds of lenses, 293 reflexion by the undulatory 
33. Refraction by lenses, 294 theory, 
34. Focus of lenses, ‘ By 294 « 92. The law of refraction similarly 
35. Divergence of rays in concave illustrated, : : 
lenses, 295 « 93-99. Preimhoters spectra, : 
36. Secondary axis of lenses, 295 « 100, 101. Polarization of light, 310, 
37-39. Images formed in lenses, 295 * 102, 103. The magic lantern, : 
40. Aperture of the lens necessary to « 104, Camera lucida, ‘ 7 
unite all rays in one point,. 295 « 105, 106. Brewster’s kaleidoscope, : 
4l, 42. Fresnel’s polyzonal lens, 295 99 
43, 44. Decomposition of light into an * 
various colored rays, . _ 996| Fig. 1. Apparatus for observing the action 
45. Composition of white light from of terrestrial magnetism on 
various colored rays, 297 vertical currents, 
46. Decomposition of the natural « 2,3. Faraday’s apparatus for observ- 
colors of bodies by the prism, 297 ing the rotative action of 
47. Achromatic prism, 297 terrestrial magnetism on 
48. Achromatic lens, 298 horizontal currents, 
49. Mosaic composite eye, 998 « 4. Action of parallel currents upon 
50. Simple human eye, 299 each other, : 
51. Illustrating double sight, 300 « 5, 6. Apparatus to show the action of 
o2. Ill’g the possibility of seeing vari- crossing currents upon each 
ous objects at once, 300 other, 
53, 54. Irradiation, . 300 «7. App’s for determining the plane of 
55. The phenakistoscope, 301 the terrestrial currents, 
56. Wollaston’s camera lucida, 302 « 8. Declination spiral wire, 
57, 58. Camera obscura, . 302 « 9,10. Ampére’s apparatus for ex- 
59. Solar microscope, 303 plaining the rotation of the 
60, 61. Compound microscope, 303 magnet, — . ; 
62. Gregorian telescope, . 305 « 11. Thermo-electric currents, 
63. Cassegrainian telescope, 305 « 12. Thermo-electric multiplier, 
64. Newtonian telescope, 305 « 13. Apparatus to show the develop- 
65, Galilean telescope, 304 ment of electricity by com- 
66. Astronomical telescope, 304 bustion, 
67. Determination of the magnifying s 14. Illustrating induction currents, 
power of telescopes, 304 « 15-17. Neef and Wagner's induction 
68. Fresnel’s apparatus for determin- coil, . 
ing the interference of « 18. Apparatus to show the pr oduction 
light, é 306 of electrical currents by 
69. Norremberg’s polariscope, ; 310 magnetism, 
70. Angle of polarization, ali! “ 19. Induction coil in connexion with 
71, 72. Rochon’s micrometer, 319 magnets, . . 
73. Soleil’s apparatus for measuring “« 20-22. Ettinghausen’s magneto- -elec- 
the rings of polarization, 313 tric rotating machine, 
74-76. Daguerreotype apparatus, 314 « 93-27. Stohrer’s triple magneto-elec- 
77. Reflexion by spherical concave tric machine, . 5 
mirrors, ‘ 988 « 98. Differential galvanometer, . , 
78. Refraction in water, . 991 « 29. Apparatus for determining the 
79. Common prism, 991 conducting powers of me- 
80. Refraction by prisms, 292 tals, . 
81. Construction of the hollow prism, 293 « 30. App’s for determining the re- 
82. The direction of emerging rays quisite qualities of conduct- 
shown to be parallel with ing wires, . 
that of entering ones, 293 « 31,32. App’s for obtaining an un- 
83. Divergence of rays emerging from alterable thermo-electric 
lenses, , b . 294 current, 
84. Convergence of rays emerging « 33-35. Thermo-electric pile, 
from lenses, . 295 « 36-38. Stéhrer’s improvement of 
85. Angle of vision, 300 Daniel’s _ electro-magnetic 
86. Vanishing of ena objects « on the machine, . 
punctum cecum, ; 300 « 39. Ritchie’s improved machine, 
87. Apparatus for exhibiting the dura- « 40. Wheatstone’s telegraph, 
tion of an impression on the « Al, 42. Steinheil’s telegraph, 
retina, 301 43-47. Illustrating Ampére’s theory 
88. Apparatus for experiments ¢ on the of the rotation of magnets, . 
interference of light, 306 « 48, 49. Astatic multiplier, 
PAGE 
306 
307 
307 
307 
308 
31] 
304 
302 
286 
347 
349 
348 
348 
349 
347 
350 
356 
306 
337 
351 
351 
352 
353 
353 
355 
356 
356 
357 
357 
357 
339 
341 
342 
344 
348 
338 
