Lectures on some recent advances in physical science : with a special lecture on force (1876)
Tait, Peter Guthrie, 1831-1901 · London : MacMillan · leaf 250
ns of long focus. We formby means of it an image of the sun of an inch or so indiameter, and place the slit of our spectroscope succes-sively on various parts of that image. It was to be expected that some very important addi-tional information would thus be obtained. Now, suchinformation you can… … absorption lines a little thicker and darker than fromsunlight as a whole, so that it appears that there isassociated with the sun-spot something which producesan excess of absorption. There is a more powerfullyabsorbing medium at the place where the sun-spotappears than at the places where faculae…
Force and energy · Heat · Matter -- Constitution · Spectrum analysis
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