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And since silvered glass gives back considerably more light than speculum metal, the stage of equalisation with lenses is reached proportionately sooner where this material is employed. The most distinctive faculty of reflectors, however, is that of bringing rays of all refrangibilities to a focus together. They are naturally achromatic.
And it is because this so vivid popular science has its issue from this 'source' it is because it proceeds from this scientific centre, on the scientific radii, through all the divergencies and refrangibilities of the universal beam it is because all this inexhaustible multiplicity and variety of particulars is threaded with the fibre of the universal science it is because all these thick-flowering imaginations, these 'mellow hangings, are hung upon the stems and branches that unite in the trunk of the prima philosophia it is because of this that men find it so prophetic, so inclusive, so magical; this is the reason they find all in it.
If we employ colours of intermediate refrangibilities, which we may do by causing the different colours of a spectrum to shine through the slit, we obtain bands of colour intermediate in width, and occupying intermediate positions, between those of the red and blue. The aspect of the bands in red, green, and violet light is represented in fig. 16.
White light, with all its constituents complete, sent through such flames, would, he inferred, have those precise constituents absorbed, whose refrangibilities are the same as those of the bright bands; so that after passing through such flames, the white light, if sufficiently intense, would have its spectrum furrowed by bands of darkness.
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