Appleton's dictionary of machines, mechanics, engine-work, and engineering : illustrated with four thousand engravings on wood ; in two volumes (1873)
D. Appleton and Company · New York : D. Appleton and Co. · leaf 618
the verysame principles, and are calculated by the same fornmlas as those given for the great lenses. In fixingthe focal distance and inclination of those subsidiary lenses, Fresnel was guided by a consideration ^.fthe necessity for keeping them sufficiently high to prevent interference with the… … Owing to certain arrangements of the apparatus which are necessary for the efficiency of the lamp,but a small portion of those rays which escape from below the lenses can be rendered available for thepurposes of a light-house; and any attempt to subject them to lenticular action, so as to add them…
Mechanical engineering · Mechanics · Engineering
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