Ragnarok : the age of fire and gravel

100 THE COMET.

ous ; they do not indicate a steady and constant pressure, such as would result where a mountainous mass of ice had caught a rock and held it, as it were, in its mighty hand, and, thus holding it steadily, had scored the rocks with it as it moved forward.

“The groove is of irregular depth, its floor rising and falling, as though hitches had occurred when it was first planed, the great chisel meeting resistance, or being thrown up at points along its path.’ 2

What other results would follow at once from contact with the comet ?

We have seen that, to produce the phenomena of the Glacial age, it was absolutely necessary that it must have been preceded by a period of heat, great enough to yaporize all the streams and lakes and a large part of the ocean. And we have seen that no mere ice-hypothesis gives us any clew to the cause of this.

Would the comet furnish us with such heat ? Let me call another witness to the stand :

In the great work of Amédée Guillemin, already cited, we read :

“On the other hand, it seems proved that the light of the comets is, in part, at least, borrowed from the sun. But may they not also possess a light of their own? And, on this last hypothesis, is this brightness owing to a kind of phosphorescence, or to the state of incandescence of the nucleus? Truly, if the nuclei of comets be incandescent, the smallness of their mass would eliminate from the danger of their contact with the earth only one element of destruction : the temperature of the terrestrial atmosphere would be raised to an elevation inimical to the existence of organized beings ; and we should only escape the danger of a mechanical shock, to run into a not less frightful

* Gratacap, “The Ice Age,” in “ Popular Science Monthly,” January, 1878, p. 321.