The method employed by the author for obtaining, by a combination of lenses, the convergence to foci of the colorific solar rays, together with the dispersion of the calorific rays, consists in making a beam of solar light, which contains both kinds of rays, pass, after it has been converged to a focus by a convex condensing lens, through a second convex lens, placed at a certain distance beyond that focus: that distance being so adjusted as that the calorific rays, which, from their smaller refrangibility, are collected into a focus more remote from the first lens than the colorific rays, and consequently nearer to the second lens, shall, on emerging from the latter, be either parallel or divergent; while the colorific rays, which, being more refrangible, had been collected into a focus nearer to the first lens, and more distant from the second, will be rendered convergent by this second lens; so that the second focus, into which they are thus collected, will exhibit a brilliant light without manifesting any sensible degree of heat. The light so obtained may be advantageously applied to the solar, and to the oxy-hydrogen microscopes, from its producing no injurious effects on objects inclosed in Canada balsam, or even on living animalcules exposed to its influence. Another improvement in the construction of the microscope employed by the author, consists in the cell for holding objects being made to move quite independently of the field glass; so that the best focus is obtained by an adjustment which does not disturb the field of view.
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Feb 1, 1912
Open Access