Читать книгу Triumphs and Wonders of the 19th Century: The True Mirror of a Phenomenal Era - James P. Boyd - Страница 36

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The great improvements in telescopes made during the century have been fruitful in two ways; a better knowledge of the surface of the moon and of the planets has been gained, and we have been enabled to learn with precision the exact motions and times of revolution of these bodies and of their accompanying moons. This information, by the use of the laws ascertained by Kepler and La Place, gives us their exact distance, dimensions, and mass. With the increase of telescopic power, the census of the starry host has been so augmented that the number of stars within reach of our modern instruments exceeds 125,000,000. But we had gone little beyond this sort of information until the invention of the spectroscope.

Previous to the year 1859 a few meteors, composed chiefly of stone or iron, some of which had been actually seen to fall from the sky, had been subjected to chemical analysis; but outside of this naught was known of the physical constitution of other worlds than ours. Our ignorance on this point was complete. All our attempts to become better acquainted with the structure of the planets, the composition of the sun, and the nature of the fixed stars would probably have been in vain but for the invention of the spectroscope. This surprising instrument is a master-key with which to unlock many of Nature’s mysteries; her recesses are brought to view, and the farthest star is subjected to an accurate chemical analysis, so far as the light that comes from it is sufficient to disclose the materials of which it is composed.

THE LICK OBSERVATORY, MOUNT HAMILTON, CALIFORNIA.

The wondrous use of electricity as an agent for the production of light, heat, and power is no greater achievement, in its way, than is Spectrum Analysis in bringing to our earthly laboratories the work of the Divine Hand performed in distant regions of space. Yet the story of the spectroscope is easily told. In its essential elements it is merely this: A ray of light, entering a darkened room through a hole in the window shutter, produces a bright beam on the opposite wall. A triangular glass prism held close to the crevice turns this beam into a band of rainbow hues. If the hole can be changed into a small slit, say one fourth of an inch high and one fiftieth of an inch wide, and if the light can further be made to pass in succession through several prisms, instead of through one, the band will be so elongated thereby that its various and surprising markings can be thoroughly traced and fully studied.

THE SPECTROSCOPE.

To this band of bright colors Sir Isaac Newton gave the name of the solar spectrum. The image formed by the light of any luminous body, after it has passed through a prism, is said to be the spectrum of that body.