234 THE POPULAR SCIENCE MONTHLY. 



Vesuvius during those lava-flows that succeed an eruption, and con- 

 tinue for weeks or months even. What haj)pens to-day, if studied 

 with a little good sense and reflection, can enlighten us on what must 

 have hapjiened eighteen centuries ago. For instance, we have seen 

 how slow lava-currents, remote from the vent of escape and cooled by- 

 contact with the ground and air, flowing around country-houses, level 

 and consume them, with a sudden flaming up of roofs and floors. How 

 could the stuccoes and the marble statues of Herculaneum remain un- 

 harmed, in their original color, free from crack or splinter, if they had 

 been enveloped in lava ? We have seen metals by mere contact melt 

 and vanish in that viscous paste, which glows like fused iron or glass 

 gushing from a furnace. How, then, do we find in Herculaneum articles 

 of silver, bronze statues, leaden vases, with their shapes, their relief, 

 their ornaments and polish uninjured ? The bronzes of Herculaneum 

 are even better preserved than those of Pompeii, being distinguished 

 by their freshness of surface, their lustre, and dark and even tone, 

 while the Pompeian bronzes have been attacked by sulphurous fumes, 

 and eaten on the surface, and have taken on an agreeable ultra-marine 

 blue tint, like that of sulphate of copper. 



Other facts of the same kind are quite as puzzling. The guides 

 amuse strangers with an experiment ; breaking off a bit of lava with an 

 iron-pointed stick, they let it cool on the ground, and stamp a penny 

 on it, to get an impression of the coin. If the trial is made too quickly, 

 the copper melts, and the coin, instead of leaving its image, disappears 

 and mingles with the rest of the lava. How, then, do we find at Her- 

 cula ,-, ~.rn so many ancient silver or copper coins, not merely un- 

 desL-^-i, but not even changed, by those waves of lava which attain 

 a concentrated heat beyond all measurement ? We know,4oo, that the 

 ancients used colors with a mineral base in decorating their buildings ; 

 they will stand dampness from the earth, but the touch of fire changes 

 their nature ; the partial fires that have left traces in Pompeii have in 

 some places altered the blue to gray, and the red to yellow, and Nea- 

 politan artists in our time well understand the very simple method of 

 producing what is called burnt-yellow, by exposing minium to the 

 action of fire. How, then, do the houses uncovered at Herculaneum 

 present such exquisite colors ? How is it that the ultra-marine blue 

 and the vermilion-red, covering whole walls, keep a freshness and 

 smoothness that contact with a burning substance must necessarily 

 have destroyed ? Then, too, on Vesuvius I have seen trees just 

 touched by the lava-flow take fire like matches, throw out a blazing jet, 

 and fall at once, as if struck with lightning. Why have the beams and 

 floors and sills of Herculaneum, instead of crumbling into ashes, slowly 

 decayed in their places in the bosom of the earth, leaving no holes nor 

 fractures ? Why are they found blackened like oak-timbers that have 

 been sunk in the mud for ages, like the piers of bridges and the piles 

 of old docks at Carthage, and the wood brought down by the Jordan 



