Fresnel recognized the advantages of a plano-convex lens to refract, in lines nearly parallel to their axis, all the rays emanating from their foci[7]. He built up the lenses in stages to correct their spherical aberration and obtain full command over the rays of a lamp[7].
The stories related by Arabs and European travelers must be very cautiously examined[1]. It may be seen, in the presented design, that catoptric apparatus is composed of nine reflectors generally arranged in groups of threes[1]. A rotatory machine sets the system in motion, and eclipses at greater or shorter intervals are obtained by the varying speed with which it's worked[1].
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