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a half. What then is the weight of the column of water, which the pressure of the atmosphere balances?
Let me see; that will be thirty-four times and a half, sixty-two and a half; that will be equal to 2158 pounds.
The one hundredth and forty-fourth part of this will be the weight of the air on every square inch. What is it? I am sure you can tell me.
What a weight it must be, Father, on the whole earth.
It must, indeed. Mr. Cotes made an inquiry on this subject, the result of which was, that it is equal to a globe of lead sixty miles in diameter; which amounts to a pressure equal to five thousand millions of millions of tons.
Does the air press on me, at the rate of fifteen pounds for every square inch of my body? I don't feel that it does, Father.
But it does; and the reason you do not feel it, is, because it is counteracted by the air that is within you. On every square inch there is a pressure of fifteen pounds; on every square foot, then, there will be 144 times as much, or 2160 pounds; and if we suppose, that there are fifteen square feet on a man's body, how much will the weight be? The answer, Frank, I think will surprize you.
That will be, fifteen times 2160; or, 32,400 pounds.
How many tons is this?
Divided by 112, it is 289 hundred; and by twenty, to bring the hundreds into tons, it is almost fourteen tons and a half.
It is. But the higher we rise above the surface of the earth, the air becomes thinner and lighter. I have read of travellers who have ascended some of the highest mountains in South America, and who have found it difficult to breathe on their summits. Had they stayed long on those eminences, they would have expired.
The purity of the air is very remarkable, Father.
It is, Frank. It was necessary that it should be so, for the preservation of health and life. Hence appears the use of winds, and tempests, and storms of thunder and lightning; these constantly promote its purification. The works of God are not only magnificent, but they are worthy of their adorable Creator, as they are all arranged in infinite wisdom and goodness.
FATHER, did you not say in our last walk, that colors were accidental, and not essential to bodies?
Yes; and so they are: a body is always of the color of those rays of light which it reflects.
Do colors, then, arise from the light?
Certainly. If there were no light, there would be no colors. You said last evening, as you looked from the drawing room window, that it was very dark; of what color was every thing then?
Black, Father; but that was, because we could not see distinctly.
You can never see any object without light; and then it is colored by the rays of the sun.
But are not the rays of the sun white, or of a light yellow, Father?
No; or else every thing would be of these colors.
But how do you know this?
I will tell you, Frank; here is a triangular glass, which is called a prism. Draw up the shutter for a few moments. Here are a few of the sun's rays, through a little passage which has been left by a nail; I will intercept them with the prism: there,
Why, Father, there are all the colors of the rainbow on the wainscot. Let me see; there is red, and orange, and yellow, and green, and blue, and indigo, and violet. O how beautiful!
Then, Father, all the colors put together would make white; would they not?
Yes; if you were to take a round piece of pasteboard, and put on the colors in proper proportion, and then turn it round swiftly, it would appear white.
In proper proportions, you say, Father ; are they not equal as seen through the prism?
No; divide the figure produced by the prism into 360 equal parts; you will find that the red will fill 45 of them; the orange, 27; the yellow, 48; the green, 60; the blue, 60; the indigo, 40; and the violet, 80.
Every ray of the sun is of a light color, Father; every ray, then, must include all the seven colors; and we should see them all, if we could refract a single ray with the prism.
Certainly; but the rays of the sun are so exquisitely fine, that you could not procure a single ray, on which to make the experiment. But as ten thousand rays, or any number you please, produce the colors of the rainbow, of course, every individual ray must produce them.
How wonderful, Father, it is, that there should be all the colors of the rainbow wrapt
up in every single ray of light! Who can find out the works of God!
It is. Here is the finger of God; here is omnipotence; here is divine wisdom.
And is there not the goodness of God, too, Father, in making creation so beautiful, to delight our eyes and to cheer our hearts?
Assuredly. Every thing might have been of one color; creation would then have lost one of its principal charms. But God's great goodness appears every where.
I want more fully to understand you, Father; you say there is no color without light.
Yes; it is the theory of Sir Isaac Newton. Then, when the geranium was shut up in the back parlor, whilst we were out last summer, and the leaves all turned white, was that for want of the light?
Certainly. The lettuce which you see evcry day on the table are white. Robert tied them up, that they might become so.
To shut out the light?
Yes, or else they would have been green; those which are not tied up, you know, are green.
Then why is one object green, and another yellow, and another red, and another violet?
The answer is easy; the rose is red, because it reflects the red rays of light, and absorbs all the other: the grass is green, because it reflects the green rays, and absorbs