Spectrum Analysis: Six Lectures, Delivered in 1868, Before the Society of Apothecaries of London

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Macmillan and Company, 1873 - 484 pages

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Page 41 - For the rays, to speak properly, are not coloured. In them there is nothing else than a certain power and disposition to stir up a sensation of this or that colour. For as sound in a bell or musical string, or other sounding body, is nothing but a trembling motion, and in the air nothing but that motion propagated from the object, and in the sensorium 'tis a sense of that motion under the form of a sound ; so colours in the object are nothing but a disposition to reflect this or that sort of rays...
Page 300 - Here one is reminded by the fleecy, infinitely delicate cloud-forms, of an English hedge-row with luxuriant elms ; here of a densely intertwined tropical forest, the intimately interwoven branches threading in all directions, the prominences generally expanding as they mount upwards, and changing slowly, indeed almost imperceptibly. By this method the smallest details of the prominences, and of the chromosphere itself, are rendered perfectly visible and easy of observation.
Page 374 - ... something of the motions of the stars relatively to our system. If the stars were moving towards or from the earth, their motion, compounded with the earth's motion, would alter to an observer on the earth the refrangibility of the light emitted by them, and consequently the lines of terrestrial substances would no longer coincide in position in the spectrum with the dark lines produced by the absorption of the vapours of the same substances existing in the stars.
Page 242 - ... these lines do not appreciably alter when the sun approaches the horizon. It does not, on the other hand, seem at all unlikely, owing to the high temperature which we must suppose the sun's atmosphere to possess, that such vapours should be present in it. Hence the observations of the solar spectrum appear to me to prove the presence of iron vapour in the solar atmosphere with as great a degree of certainty as we can attain in any question of natural science.
Page 219 - A, which can be removed at pleasure. Below the prism is an achromatic eye-piece, having an adjustable slit between the two lenses ; the upper lens being furnished with a screw motion to focus the slit. A side slit, capable of adjustment, admits, when required, a second beam of light from any object whose spectrum it is desired to compare with that of the object placed on the stage of the Microscope. This second beam of light strikes against a very small prism suitably placed inside the apparatus,...
Page 41 - The homogeneal light and rays which appear red, or rather make objects appear so, I call rubrific or red-making; those which make objects appear yellow, green, blue, and violet, I call yellowmaking, green-making, blue-making, violet-making, and so of the rest.
Page 414 - Pliicker states that when an induction spark of great heating power is employed, the lines expand so as to unite and form an undivided band. Even when the duplicity exists, the eye ceases to have the power to distinguish the component lines, if the intensity of the light be greatly diminished.
Page 429 - Vega, a Cygni, show a motion of approach. There are in the stars already observed exceptions to this general statement ; and there are some other considerations which appear to show that the sun's motion in space is not the only, or even in all cases, as it may .be found, the chief cause of the observed proper motions of the stars*.
Page 36 - ... rule exactly in such a posture that the refractions of the rays at their emergence out of the prism might be equal to that at their incidence on it. This prism had some veins running along within the glass from one end to the other, which scattered some of the sun's light irregularly, but had no sensible effect in increasing the length of the coloured spectrum. For I tried the same experiment with other prisms with the same success ; and particularly with a prism which seemed free from such veins,...
Page 172 - ... can be most accurately noted. The light which is given off by the flame in this process is most intense ; indeed, a more magnificent example of combustion in oxygen cannot be imagined— and a cursory examination of the flame spectrum in its various phases reveals complicated masses of dark absorption bands and bright lines, showing that a variety of substances are present in the flame in the state of incandescent gas.

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