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Most of the British and French observation balloons have been of the old-fashioned spherical form which officers in those services find sufficiently effective. The Germans, however, claimed that a balloon might be devised which would not be so very unstable in gusty weather. Out of this belief grew the Parseval-Siegfeld balloon which from its form took the name of the Sausage.
The middle, which supplied most of its height, was a long, round tower, and at top there was a spherical pinnacle which had what looked to be a room in it.
The rays that pass near the outer edge of the lens have a shorter focus than that of the rays which pass near the center of the lens; this is called spherical aberration. A similar phenomenon occurs with a concave mirror whose surface is spherical. In that case, as we have seen, the difficulty is overcome by giving the mirror a parabolic instead of a spherical form.
This is well illustrated by a simple experiment with a tuning fork and a spherical resonator reinforcing the tone of the fork. When the fork is struck, the ear hears the sound issuing from the resonator, not that coming direct from the fork. This is brought out distinctly by placing the fork at a little distance from the resonator.
If the human mind, ordained by an omniscient Creator, had been intended to be what it has become, exacting, inquiring, agitated, tormented so different from mere animal thought and resignation would the world which was created to receive the beings which we now are have been this unpleasant little park for small game, this salad patch, this wooded, rocky and spherical kitchen garden where your improvident Providence had destined us to live naked, in caves or under trees, nourished on the flesh of slaughtered animals, our brethren, or on raw vegetables nourished by the sun and the rain?
How I longed to discover the secret of some perfect lens whose magnifying power should be limited only by the resolvability of the object, and which at the same time should be free from spherical and chromatic aberrations, in short from all the obstacles over which the poor microscopist finds himself continually stumbling!
Rolling over and over, with the legs frequently in the air, it raised waves that rocked my little boat and made shooting difficult; but upon a close approach, taking good care to keep out of the reach of its struggles, I gave it a quietus with a hardened spherical ball from the same rifle, which passed right through the head.
The great brown cloud quickly began to lose its spherical form, part of it descending heavily to the earth, and part floating away in vast dust-clouds borne inland by the breeze, settling downward as they moved, and depositing on land, water, ships, houses, domes, and trees an almost impalpable powder.
All natural forms strive for the spherical. The waves on the beach curve and roll and make the pebbles round. From the drops of rain and dew to the mighty celestial orbs one law prevails. Nature works to no special ends; she works to all ends; and her harmony results from her universality.
The current was applied and the great spherical mass apparently disappeared, being transformed instantly into the transparent metal arenak. Then indeed had the Earth-men a vehicle such as had never been seen before!
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