|
Main
- books.jibble.org
My Books
- IRC Hacks
Misc. Articles
- Meaning of Jibble
- M4 Su Doku
- Computer Scrapbooking
- Setting up Java
- Bootable Java
- Cookies in Java
- Dynamic Graphs
- Social Shakespeare
External Links
- Paul Mutton
- Jibble Photo Gallery
- Jibble Forums
- Google Landmarks
- Jibble Shop
- Free Books
- Intershot Ltd
|
books.jibble.org
Previous Page
| Next Page
Page 13
The sunshine says to the sea, held in the grasp of gravitation,
"Rise from your bed! Let millions of tons of water fly on the wings
of the viewless air, hundreds of miles to the distant mountains,
and pour there those millions of tons that shall refresh a whole
continent, and shall gather in rivers fitted to bear the commerce
and the navies of nations." Gravitation says, "I will hold every
particle of this ocean as near the centre of the earth as I can."
Sunshine speaks with its word of power, and says, "Up and away!"
And in the wreathing mists of morning these myriads of tons rise
in the air, flyaway hundreds of miles, and supply all the Niagaras,
Mississippis and Amazons of earth. The sun says to the earth, wrapped
in the mantle of winter, [Page 36] "Bloom again;" and the snows
melt, the ice retires, and vegetation breaks forth, birds sing, and
spring is about us.
Thus it is evident that every force is constitutionally arranged
to be overcome by a higher, and all by the highest. Gravitation of
earth naturally and legitimately yields to the power of the sun's
heat, and then the waters fly into the clouds. It as naturally
and legitimately yields to the power of mind, and the waters of the
Red Sea are divided and stand "upright as an heap." Water naturally
bursts into flame when a bit of potassium is thrown into it, and
as naturally when Elijah calls the right kind of fire from above.
What seems a miracle, and in contravention of law, is only the
constitutional exercise of higher force over forces organized to
be swayed. If law were perfectly rigid, there could be but one
force; but many grades exist from cohesion to mind and spirit.
The highest forces are meant to have victory, and thus give the
highest order and perfectness.
Across the astronomic spaces reach all these powers, making creation
a perpetual process rather than a single act. It almost seems as
if light, in its varied capacities, were the embodiment of God's
creative power; as if, having said, "Let there be light," he need do
nothing else, but allow it to carry forward the creative processes
to the end of time. It was Newton, one of the earliest and most
acute investigators in this study of light, who said, "I seem to
have wandered on the shore of Truth's great ocean, and to have
gathered a few pebbles more beautiful than common; but the vast
ocean itself rolls before me undiscovered and unexplored."
[Page 37]
EXPERIMENTS WITH LIGHT.
A light set in a room is seen from every place; hence light streams
in every possible direction. If put in the centre of a hollow sphere,
every point of the surface will be equally illumined. If put in
a sphere of twice the diameter, the same light will fall on all
the larger surface. The surfaces of spheres are as the squares
of their diameters; hence, in the larger sphere the surface is
illumined only one-quarter as much as the smaller. The same is true
of large and small rooms. In Fig. 7 it is apparent that the light
that falls on the first square is spread, at twice the distance,
over the second square, which is four times as large, and at three
times the distance over nine times the surface. The varying amount
of light received by each planet is also shown in fractions above
each world, the amount received by the earth being 1.
[Illustration: Fig. 7.]
[Illustration: Fig. 8.--Measuring Intensities of Light.]
The intensity of light is easily measured. Let two lights of different
brightness, as in Fig. 8, cast shadows on the same screen. Arrange
them as to distance so that both shadows shall be equally dark.
Let them fall side by side, and study them carefully. Measure the
respective distances. Suppose one is twenty inches, the other forty.
Light varies as the square [Page 38] of the distance: the square of
20 is 400, of 40 is 1600. Divide 1600 by 400, and the result is that
one light is four times as bright as the other.
[Illustration: Fig. 9.--Reflection and Diffusion of Light.]
Light can be handled, directed, and bent, as well as iron bars.
Darken a room and admit a beam of sunlight through a shutter, or
a ray of lamp-light through the key-hole. If there is dust in the
room it will be observed that light goes in straight lines. Because
of this men are able to arrange houses and trees in rows, the hunter
aims his rifle correctly, and the astronomer projects straight
lines to infinity. Take a hand-mirror, or better, a piece of glass
coated on one side with black varnish, and you can send your ray
anywhere. By using two mirrors, or having an assistant and using
several, you can cause a ray of light to turn as many corners as you
please. I once saw Mr. Tyndall send a ray into a glass jar filled
with smoke (Fig. 9). Admitting a slender ray through a small hole in
a card over the mouth, one ray appeared; removing the cover, the
whole jar was luminous; as the smoke disappeared in spots cavities
of darkness appeared. Turn the same ray into a tumbler of water,
[Page 39]
it becomes faintly visible; stir into it a teaspoonful of milk, then
turn in the ray of sunlight, and it glows like a lamp, illuminating
the whole room. These experiments show how the straight rays of
the sun are diffused in every direction over the earth.
Previous Page
| Next Page
|
|