Jules Verne,
Journey into the Interior of the Earth…
(1877)
“ This roof itself is formed of fragments of rock carried down, of enormous stones, as if by some giant's hand; but at one time the expulsive force was greater than usual, and this block, like the falling keystone of a ruined arch, has slipped down to the ground and blocked up the way. It is only an accidental obstruction, not met by Saknussemm, and if we don't destroy it we shall be unworthy to reach the centre of the earth. ”
