But with the help of this outflow the thickness of the crust of the island increased materially, and therefore also its powers of resistance. It may easily be conceived what vast quantities of elastic gases, what masses of molten matter accumulated beneath its solid surface whilst no exit was practicable after the cooling of the trachytic crust. Therefore a time would come when the elastic and explosive forces of the imprisoned gases would upheave this ponderous cover and drive out for themselves openings through tall chimneys. Hence then the volcano would distend and lift up the crust, and then burst through a crater suddenly formed at the summit or thinnest part of the volcano. To the eruption succeeded other volcanic phenomena. Through the outlets now made first escaped the ejected basalt of which the plain we had just left presented such marvellous specimens. We were moving over grey rocks of dense and massive formation, which in cooling had formed into hexagonal prisms. Everywhere around us we saw truncated cones, formerly so many fiery mouths. After the exhaustion of the basalt, the volcano, the power of which grew by the extinction of the lesser craters, supplied an egress to lava, ashes, and scoriae, of which I could see lengthened screes streaming down the sides of the mountain like flowing hair. Such was the succession of phenomena which produced Iceland, all arising from the action of internal fire; and to suppose that the mass within did not still exist in a state of liquid incandescence was absurd; and nothing could surpass the absurdity of fancying that it was possible to reach the earth's centre. So I felt a little comforted as we advanced to the assault of Snæfell. The way was growing more and more arduous, the ascent steeper and steeper; the loose fragments of rock trembled beneath us, and the utmost care was needed to avoid dangerous falls. Hans went on as quietly as if he were on level ground; sometimes he disappeared altogether behind the huge blocks, then a shrill whistle would direct us on our way to him. Sometimes he would halt, pick up a few bits of stone, build them up into a recognisable form, and thus made landmarks to guide us in our way back. A very wise precaution in itself, but, as things turned out, quite useless. Three hours' fatiguing march had only brought us to the base of the mountain. There Hans bid us come to a halt, and a hasty breakfast was served out. My uncle swallowed two mouthfuls at a time to get on faster. But, whether he liked it or not, this was a rest as well as a breakfast hour and he had to wait till it pleased our guide to move on, which came to pass in an hour. The three Icelanders, just as taciturn as their comrade the hunter, never spoke, and ate their breakfasts in silence.