MARINE EIRE.

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Copper, after three minutes exposure, was found to havelost in weight. Iron, shear-steel. What is remarkable inthis experiment is, the lower part in contact with the char-coal, was first melted, while that part which was ex-posed to the focus remained unfused; an evidence of theeffect of flux in this metal; and likewise, perhaps, also insupport of a previous suggestion, that the melting point, orwhere the greatest heat is found, is beyond the surface ofthe focus.

In iron scoria, and turnings of iron, the scoria first wasoperated upon, and before the turnings, contrary to expec-tation. Calx of iron, from vitriolic acid, precipitated by amild alkali before exposure, weighed 5i grains, increasedin weight a quarter of a grain, indicating that the increasewas occasioned by the absorption of caloric.

Experiments were also made on regulus of zinc, cobalt,bismuth, antimony, and a variety of other substances, witha great variety of effects; but all tending to establish someuseful knowledge with respect to the nature of those sub-stances, and the power of intense solar fire upon them.The result of the experiment on 33 grains of fine kearsh,taken from the canuon foundry, was, that it evaporatedvery fast during 120', when there remained only 11 grains;after an exposure of 150", the residuum began to flow intosmall globules, which, when cold, were attracted by themagnet: this is said to be a proof in support of the vastsuperiority of this lens over the heat of any furnace yetknown.

From what has appeared, it is hoped, that the immenseimportance of this instrument, when well constructed, in allcases where intense heat is required, beyond any othermeans of obtaining it, will be sufficiently apparent. Witha view to assist the arts, we have been thus circumstantial.

MARINE FIRE.

Marine Fire, called also Greek Fire, (in French, FeuGregeois, ) because first used by the Greeks, about the year660,under Constantine Pagonatus, against the Saracens, underCizicus, in the Hellespont , with such effect that they burntthe whole Saracen fleet, in which were 30,000 men.

Concerning the true nature of this fire, the moderns arealtogether unacquainted; the inventors keeping the modeof its preparation an impenetrable secret. Thus this, andnumerous curious arts, have been lost to posterity: the only

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