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136 watch in hand, leaning against the railings, and waiting with impatience the moment when true solar noon is indicated by the sharp report of the little piece. Their belief in the correctness of solar time is something astonishing; and if a bystander were to insinuate, no matter how delicately, that solar time varied slightly every now and then, he would either receive a smile of pitying contempt, or else he would be called out upon the spot. Fig. 34 gives a pretty view of the celebrated cannon of the Palais Royal.

We now come to another application of the refracting power of lenses, in the way of concentrating rays, which is infinitely more valuable to humanity than

either of those we have just mentioned; we mean the construction of enormous refracting apparatuses for lighthouse purposes. The first lighthouse of which we