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

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Macmillan, 1870 - 404 pages
 

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Page 94 - The colours thus communicated by the different bases to flame afford, in many cases, a ready and neat way of detecting extremely minute quantities of them...
Page 37 - ... 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 more copiously than the rest...
Page 31 - ... 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 decaying and vanishing by degrees.
Page 31 - ... 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 fixed 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 the rays into the prism, and at their going out of it, were equal to one another.
Page 193 - 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 159 - ... doubt, and that which previously depended upon the quickness of vision of a skilled eye has become a simple matter of exact scientific observation. The light which is given off by the Bessemer flame is most intense, — indeed, a more magnificent example of combustion in oxygen cannot be imagined. 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...
Page 37 - 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. And if at any time I speak of light and rays as coloured or endued with colours, I would be understood to speak not philosophically...
Page 35 - For by this refraction the colour of the light was never changed in the least. If any part of the red light was refracted, it remained totally of the same red colour as before. No orange, no yellow, no green or blue, no other new colour was produced by that refraction.
Page 184 - Frankland has recently shown that, when hydrogen gas is burnt in oxygen gas under a pressure gradually increasing up to twenty atmospheres, the feeble luminosity of the flame becomes gradually augmented, until at a pressure of ten atmospheres the light emitted by a jet about one inch long is amply sufficient to enable an observer to read a newspaper at a distance of two feet from the flame. Examined by the spectroscope the spectrum of this flame is bright and perfectly continuous from red to violet....
Page 318 - In a direction at right angles to that of the slit, an opening of about -^ inch was left between the pieces of glass for the passage of the pencils from the object-glass. By means of this arrangement the spectrum of a star is seen accompanied by two spectra of comparison, one appearing above and the other below it. As the reflecting surfaces are about 0'5 inch from the slit, and the rays from the spark are divergent, the light reflected from the pieces of glass will have encroached upon the pencils...

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