" ... In order to bring the world into the form which it now bears, it was not mere sculpture that was needed; the mountains could not stand for a day unless they were formed of materials altogether different from those which constitute the lower hills and the surfaces of the valleys. A harder substance had to be prepared for every mountain-chain, yet not so hard but that it might be capable of crumbling down into earth, fit to nourish the Alpine forest and the Alpine flowers; not so hard but that in the midst of the utmost majesty of its enthroned strength there should be seen on it the seal of death, and the writing of the same sentence that had gone forth against the human frame, 'Dust thou art and unto dust thou shalt return.' And with this perishable substance the most majestic forms were to be framed that were consistent with the safety of man, and the peak was to be lifted and the cliff rent as high and as steeply as was possible, in order yet to permit the shepherd to feed his flocks upon the slope, and the cottage to nestle beneath their shadow."[24] [24] Modern Painters. CHAPTER VIII. VOLCANIC MOUNTAINS. 'Tis said Enceladus' huge frame, Heart-stricken by the avenging flame, Is prisoned here, and underneath Gasps through each vent his sulphurous breath; And still as his tired side shifts round, Trinacia echoes to the sound Through all its length, while clouds of smoke The living soul of ether choke. VIRGIL: _Æneid iii._ In some parts of the world we meet with mountains of a very different kind from any we have yet considered,--mountains that are known at times to send forth fiery streams of glowing lava, and to emit with terrific force great clouds of steam. Such mountains have long been known, in popular but unscientific language, as "burning mountains,"[25]--a term which is unfortunate, because they do not burn in the proper sense of the word, like candles or gas-jets. They are better known as volcanoes. There are about three hundred and fifty known active volcanoes; and if we include all mountains that once were in that state, the number is about one thousand. [25] See papers by the writer on Volcanoes and Volcanic Action in "Knowledge" for May and June, 1891, on which this chapter is partly based. Such mountains are connected in a curious way with those upheaved ridges of the world known as mountain-chains (see chap. vi., p. 191). And not only are many mountains more or less penetrated and intersected by rocks of an igneous origin (see chap. v., p. 155), but some have been largely formed by the action of old volcanoes. In fact, there are hills in Great Britain and parts of Europe, in America, and other countries, that once were actual volcanoes (see page 277).