And we are further told that, "when it, carbureted hydrogen, is mixed in due proportion with oxygen or atmospheric air, a compound is produced which explodes with the electric spark or the approach of flame." Another form of carbureted hydrogen, olefiant gas, is deadly to life, burns with a white light, and when mixed with three or four volumes of oxygen, or ten or twelve of air, it explodes with terrific violence. We shall see, hereafter, that many of the legends tell us that, as the comet approached the earth, that is, as it entered our atmosphere and combined with it, it gave forth world-appalling noises, thunders beyond all earthly thunders, roarings, howlings, and hissings, that shook the globe. If a comet did come, surrounded by volumes of carbureted hydrogen, or carbon combined with hydrogen, the moment it reached far enough into our atmosphere to supply it with the requisite amount of oxygen or atmospheric air, precisely such dreadful explosions would occur, accompanied by noises similar to those described in the legends. Let us go a step further: Let us try to conceive the effects of the fall of the material of the comet upon the earth. We have seen terrible rain-storms, hail-storms, snow-storms; [1. "American Cyclopædia," vol. iii, p. 776.] {p. 107} but fancy a storm of stones and gravel and clay-dust!--not a mere shower either, but falling in black masses, darkening the heavens, vast enough to cover the world in many places hundreds of feet in thickness; leveling valleys, tearing away and grinding down hills, changing the whole aspect of the habitable globe. Without and above it roars the earthquaking voice of the terrible explosions; through the drifts of _débris_ glimpses are caught of the glaring and burning monster; while through all and over all is an unearthly heat, under which rivers, ponds, lakes, springs, disappear as if by magic. Now, reader, try to grasp the meaning of all this description. Do not merely read the words. To read aright, upon any subject, you must read below the words, above the words, and take in all the relations that surround the words. So read this record. Look out at the scene around you. Here are trees fifty feet high. Imagine an instantaneous descent of granite-sand and gravel sufficient to smash and crush these trees to the ground, to bury their trunks, and to cover the earth one hundred to five hundred feet higher than the elevation to which their tops now reach! And this not alone here in your garden, or over your farm, or over your township, or over your county, or over your State; but over the whole continent in which you dwell--in short, over the greater part of the habitable world!