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Y

Year, its length, how measured, i. 190. Gregorian,
what meant by, i. 192. The beginning of, changed
from the 25th of March to the 1st of January, i.

193.

Z

Zenith, that point of the heavens over one's head.
Zinc, experiment with, iii. 243.

Zodiac, a belt in the heavens, sixteen degrees broad,
through which the ecliptic runs. Signs of, i. 135.
Dr. Watts's lines on, i. 136.

1

CONTENTS OF VOL. III.

Conversation

OPTICS.

I. Light: the Smallness and Velocity of its
Particles

II. Rays of Light :-Reflection and Refraction
III. Refraction of Light

IV. Refraction and Reflection of Light
V. Different kinds of Lenses

VI. Parallel, diverging, and converging Rays
VII. Images of Objects-Scioptric Ball, &c.
VIII. Nature and Advantages of Light

IX. Colours

X.

Reflected Light and Plain Mirrors
Concave Mirrors

XI.

XII. Concave Mirrors-Experiments
XIII. Concave and Convex Mirrors

XIV. Optical Deceptions, Anamorphoses, &c.

XV. Different parts of the Eye
XVI. Manner of Vision

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XVII. Spectacles, and their Uses
XVIII. Rainbow

XIX. Refracting Telescopes
XX. Reflecting Telescopes

XXI. Microscope
XXII.

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59

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1.19

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J. Bower. sc.

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