WCOIRDM PwWDE 
CONTENTS. 
Plate 19—(Continued.) 
. 92. Illustrating the manner of com- 
municating vibrations to the 
gin,’ . 
93. Ill’g the echo in “arched rooms, 
94. Hearing tube, 
95. Illustrating the metal tongue, 
96, 97. Tongue work of the organ, 
98. Illustrating the nature of the 
human voice, : ; 
PLATE 20. .5- 
. Attraction of a natural magnet, 
. Att’n of an artificial magnet, 
. Curves of filings over a magnet, 
. Influence of a magnet on an iron 
rou, ; : 
The same without contact, 
. Magnetic needle, F 
The various poles of a magnet, 
Compass, : 
Variation of the GGmpuss; 
10. Inclination of the compass, 
. Action of the earth upon the 
magnetic needle, : 
12. Intensity compass of Gambey, 
14. Coulomb’s torsion balance, 
. Coulomb’s determination of the 
strength of the magnet at 
various distances from its 
pole, 
17. Duhamel’s method of prepar- 
ing artificial magnets, 
. @pinus’s method of “doing the 
same, ; 
. Horse-shoe magnet, 
91. Armature of natural magnets, 
. Electrical pendulum, 
. Coulomb’s electroscope, 
. Pith ball electroscopes, 
. Electric pistol, 
. Volta’s straw electrometer, 
28. The electrophorus, 
. Plate electric machine, s 
30a. Rubbers of the same, . 
. Van Marum’s electric machine, . 
. Nairne’s electric machine, . 
. Franklin plate, . 
. Discharging rod, 
36. Leyden jars, 
. Electrical battery, 
. Henley’s universal discharger, 
. Electrical mortar, : 
. Kinnersley’s thermometer, . 
. Leyden jar with movable coatings, 
. Lightning wae 
. Lightning tube, 
. Electrical light, 
. Wheatstone’s apparatus for deter- 
mining the velocity of elec- 
tricity, 
. Electric wheel, . 
[By mistake of the engraver this 
figure isnumbered 76. It stands 
in the centre of the plate. ] 
. Influence of Galvanism, 
. Volta’s galvanic double plate, 
. Voltaic pile, : ; : 
50, 51. Fechner’s improvement of 
Bohnenberger’s electrometer, 
52. Trough apparatus, : 
PAGE 
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4£E 
PLATE 20—(Continued.) 
. 53-55. Wollaston’s battery, 
56. Volta’s simple galvanic series, 
57. Hare’s calorimeter, 
58. Becquerel’s constant battery, 
59, 60. Daniel’s Do. 
61. Grove’s battery, 2 
62, 68. Bunsen’s carbon battery, 
64, 65. Apparatus for ae 
water, 
66. App’s for decomposing salts, 
67. Beequerel’s galvanoplastic ap- 
paratus, 
68. Influence of the galvanic current 
on the magnetic needle, 
69. Schweigger’s galvanometer, 
70. Nobili’s improved do. 
71-74. Tangent compass, 
75. Sine compass, 
76. [See 46.] 
76-78. Magnetic action of the Baly as 
nic current, : 
79-81. Electro-magnets, 
82. Rotation of the magnet ander the 
influence of the galvanic cur- 
rent, 
83-85. Ampére’ s apparatus for deter- 
mining the influence of ter- 
restrial magnetism on the 
galvanic current, 
Neutralization of terrestrial mag- 
netism, 
87. Rotation of Ronen! currents, 
88. De la Rive’s apparatus showing 
that feeble currents are atf- 
fected by magnetism, . 
89, 90. Disconnecting and severing 
of magnetic currents, . 
86. 
PLATE 21. 
. 1. Refraction of light in its passage 
from water into air, . J 
2, 3. Full shadow and half shadow, . 
4. Inverted image caused by a ray of 
light entering a dark room 
through a small aperture, 
5. Angle of reflection of light, . 
6. Apparatus to prove the equality of 
the angles of reflection and 
of incidence, ; 
7. Proof of the symmetry of images 
reflected by plane mirrors, . 
8. Construction of reflected images, . 
9. Mirrors placed together at an 
angle, : 285, 
10-12. Wollaston’s ace gonio- 
meter, 
13. Gambey’s coniometer, 
14, 15. Reflecting sextant, 
16-18. Coneave mirror, 
19, 20. Nature of images formed in 
concave mirrors, 
. Spherical convex mirror, 
. Image formed on the same, 
. Caustic curve, 
. Angle of refraction, 
. Laws of refraction, 
. Total reflection, 
. Prism:stand, 
. Solar spectrum, 
. Prismatie refraction, 
286 
286 
287 
287 
288 
289 
289 
289 
290 
290 
290 
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