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The poetical and scientific natures rarely coexist; Haller and Goethe are examples which show that such a union may occur, but as a rule the poet is contented with the colors of the rainbow and leaves the study of Fraunhofer's lines to the man of science. Though far from being a man of science, Emerson was a realist in the best sense of that word.
I tell you, sir, that I have a brain of my own and that I should feel myself to be a snob and a slave if I did not use it. If it pleases you to believe this rigmarole about ether and Fraunhofer's lines upon the spectrum, do so by all means, but do not ask one who is older and wiser than yourself to share in your folly.
Wollaston, but they were afterwards multiplied and measured by Fraunhofer with such masterly skill, that they are now universally known as Fraunhofer's lines. To give an explanation of these lines was, as I have said, a problem which long challenged the attention of philosophers, and to Professor Kirchhoff belongs the honour of having first conquered this problem.
Fraunhofer's device of using a cylindrical lens for the purpose of giving a second dimension to stellar spectra was adopted by all, and was, indeed, indispensable. For a luminous point, such as a star appears, becomes, when viewed through a prism, a variegated line, which, until broadened into a band by the intervention of a cylindrical lens, is all but useless for purposes of research.
"Sir, I have read with amusement, not wholly unmixed with some less complimentary emotion, the complacent and wholly fatuous letter of James Wilson MacPhail which has lately appeared in your columns upon the subject of the blurring of Fraunhofer's lines in the spectra both of the planets and of the fixed stars. He dismisses the matter as of no significance.
In his second paper, communicated to the Berlin Academy before the close of 1859, Kirchhoff proved the existence of iron in the sun. The bright lines of the spectrum of iron vapour are exceedingly numerous, and 65 of them were subsequently proved by Kirchhoff to be absolutely identical in position with 65 dark Fraunhofer's lines.
Kirchhoff saw that from the agreement of the lines in the spectra of terrestrial substances with Fraunhofer's lines, the presence of these substances in the sun and fixed stars might be immediately inferred.
The rays emitted from the white-hot substance of the sun have to pass, before reaching our earth, through the sun's atmosphere, and since the light emitted from any incandescent body is absorbed on passing through the vapour of that substance, and since the sun is surrounded by such an atmosphere of the vapours of various metals and substances, hence we have, on examining the sun's spectrum, instead of coloured bands or lines only, many dark ones amongst them, which are called Fraunhofer's lines.
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