nsequently the beam of re- In Professor Balestrieri’s apparatus the focal point is ar- flected light will be composed of parallel rays, bitrary, and the segments can be adjusted to suit it at any sy - Fig. 4 represents a section of an assemblage of these re- position, to give, say, a focal distance… … For lighthouses, at the present time the Fresnel lens is set of segments, or at most two, would replace the dozen largely employed; but this is subject to the disadvantages parts, 1, 2, 3, 1’, 2’, 3’, etc. Take any point on the line, A B, lenticular systems, besides affording a greater simplicity…
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