The Spectroscope and Its Work

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Society for Promoting Christian Knowledge, 1910 - 163 pages
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Page 28 - In a very dark Chamber at a round hole about one third part of an Inch broad made in the Shut of a Window I placed a Glass Prism, whereby the beam of the Sun's Light which came in at that hole might be refracted upwards toward the opposite Wall of the Chamber, and there form a coloured Image of the Sun.
Page 28 - ... is described. The prism therefore being placed in this posture, I let the refracted light fall perpendicularly upon a sheet of white paper at the opposite wall of the chamber, and observed the figure and dimensions of the solar image formed on the paper by that light. This image was oblong and not oval, but terminated with two rectilinear and parallel sides, and two semicircular ends. On its sides it was bounded pretty distinctly, but on its ends very confusedly and indistinctly, the light there...
Page 62 - Its spectrum is marked, as is known, in its whole extent by a multitude of irregularly grouped luminous lines: but among these may be remarked a double line situated at the boundary of the yellow and orange. As this double line recalled by its form and situation the line D of the solar spectrum, I wished to try if it corresponded to it; and in default of instruments for measuring the angles, I had recourse to a particular process. "I caused an image of the sun, formed by a converging lens, to fall...
Page 65 - Hence this coincidence,' says Kirchhoff, ' must be produced by some cause, and a cause can be assigned which affords a perfect explanation of the phenomenon. The observed phenomenon may be explained by the supposition that the rays of light which form the solar spectrum have passed through the vapour of iron, and have thus suffered the absorption which the vapour of iron must exert. As this is the only assignable cause of this coincidence, the supposition appears to be a necessary one.
Page 62 - Thus the arc presents us with a medium which emits the rays D on its own account, and which at the same time absorbs them when they come from another quarter.
Page 107 - ... or 3" wide, brighter and closer together where the pillars had formerly stood, and rapidly ascending. ' When I first looked some of them had already reached a height of nearly 4...
Page 29 - ... about two inches and the eighth part of an inch, including the penumbra. For the image was eighteen feet and a half distant from the prism; and at this distance that breadth, if diminished by the diameter of the hole in the window-shut, that is by a quarter of an inch, subtended an angle at the prism of about half a degree, which is the sun's apparent diameter. But the length of the image was about ten inches and a quarter, and the length of the rectilinear sides about eight inches, and the refracting...
Page 78 - A rational classification of the stars according to their spectra is probably only to be obtained by proceeding from the standpoint that the phase of development of the particular body is in general mirrored in its spectrum.
Page 28 - ... following experiments perpendicular to the incident rays. About this axis I turned the prism slowly, and saw the refracted light on the wall or coloured image of the sun first to descend, and then to ascend. Between the descent and ascent when the image seemed stationary, I stopped the prism and fix'd it in that posture, that it should be moved no more. For in that posture the refractions of the light at the two sides of the refracting angle, that is at the entrance of it, were equal to one another.
Page 30 - PT was coloured, being red at its least refracted end T, and violet at its most refracted end P, and yellow, green, and blue in the intermediate spaces. Which agrees with the proposition that lights which differ in colour do also differ in refrangibility.

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