The problem was thus solved, and proof obtained that dew ascended from the earth. To the joy, however, of some, a doubt presented itself. By renewed experiments it was found that this dew from the earth did not equally affect all bodies, and was partial in its bearing. For instance, it appeared to avoid gold, silver, metal, and polished marbles; while it adhered to glass, oily and resinous substances.
Place a gold or plated vessel under a crystal vase in a garden during the night, and in the morning you will find the edges perfectly dry, while the crystal vase will be wet. The cause of this difference is not accounted for. Reaumur supposes, but does not affirm, that the golden vessel, containing more caloric than the crystal, repels the dew, while the latter attracts it.
In confirmation of this supposition, Reaumur proposed the following experiment. Place a china cup upon a stone within a hot-bed; and further on, and beyond the influence of the hot-bed, another cup of similar form, substance, and diameter; this will be charged with dew, the other will remain dry. In explanation of this difference, it may be imagined that the phenomenon of which they sought the solution, originated in electricity; an opinion, however, which has no influence over the main discovery that dews arise from the ground, instead of falling from the skies, as asserted by the mythology of the ancients, and the tropes of Scripture.
CHAPTER XIV.
PERPETUAL LAMPS AND ARCHIMEDES.
Stability is not the characteristic of man or his works. The discovery of perpetual motion has long been the object of our ambition; the sole approach to which appears to be our futile perseverance in the pursuit. Let us be content, therefore, with aspiring to duration, a sufficient triumph for perishable man; and be it noted that this quality, though impressed by human art upon inert matter, such as the Pyramids of Egypt, is incompatible with the mutability of our social institutions.
The word perpetual has been too often and too easily applied. The marvellous is too often substituted for the true, just as great vices are more widely apparent than great virtues. Who has not heard, for instance, of perpetual lamps, miraculous as the Wonderful Lamp of the Arabian Tales!
The Pagan priesthood originated these fabulous sepulchral lights; and those of our own faith who had the weakness to adopt their deception, endangered our confidence by recourse to unworthy trickeries. Pausanias mentions a lamp of massive gold, consecrated by Callimachus, and endowed with such properties as to endure a year without deterioration. Another is said to have existed in a temple in England. Pope Gelasius affirms, in the acts of St. Sylvester, that in the Baptistery of Rome, there was a lamp which had burned without intermission since the reign of Constantine, viz., half a century. That the dark ages should have admitted such marvels is not surprising. But one of the illuminati of the sixteenth century, Fortunio Liceti, composed a treaty concerning the existence of such lamps, asserting that, upon opening the tomb of the giant Pallas, a lamp was found which had been burning since the times of the pious Æneas. Another was stated to have been found in the tomb of Tullia, during the Pontificate of Paulinus, about fifteen centuries and a half after its construction. In the reign of Justinian, a portrait of our Saviour was discovered at Edessa with a lamp unrenovated from the period of the Christian era, that is, during a period of five centuries. Fortunio cites a vast number of similar examples; from which he infers that the Romans possessed the secret of making inextinguishable lamps. His conviction upon the subject is such, that he attempts to explain the possibility by a theory that the combustion of the smoke produced fresh oil for the nourishment of the lamp. This must surely have been the far-famed oil of the Phœnix.