Page:The fairy tales of science.djvu/207

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Great Geyser is an irregular oval, about fifty-six feet by forty-six, formed of a mound of flinty deposits about seven feet high. The channel through which the water is ejected is about sixteen feet in diameter at the opening, but it contracts to ten feet lower down; its depth is estimated at sixty feet.

From experiments made by the Chevalier Bunsen, in 1846, it appears that the Geysers are irregular tubes fed with rain and snow-water, and that their peculiar form favours the heating of the lower portions of the contained water, by the subterranean fires, to a degree far above the boiling point. The eruption of one of these Geysers is explained by supposing that when the whole of the contained water is sufficiently heated to allow of ebullition towards the upper part of the tube, portion after portion of the highly heated water successively bursts into steam as the pressure is diminished by the removal of the upper portion of the aqueous column.

That this is the true explanation of the phenomena is highly probable, since artificial Geysers have been constructed of iron tubes, which being filled with water, and heated near the lower extremity by burning charcoal, eject little columns of boiling water, and mimic all the phenomena presented by the natural Geysers.

Let us now ring the bell, and tell Mary to take away the tea-kettle, for there is no knowing what abstruse subjects it may suggest, as it sits on the