نبذة مختصرة : MAY I call your attention to an error which has occurred in the engraving of the Spectrum of the Aurora which I sent you last week. The lines are marked in strength exactly the reverse of what they should be. Thus: No. 1 is the strongest, and is a sharp line easily seen, and in the drawing it is the weakest; and so with the others. No. I is the brightest, No. 5 is the faintest.
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