As you walk round the city walls[121], and see how the volcanic matter is piled upon it in one heap, it looks as though the hand of man had purposely buried it, by carrying and throwing over it the volcanic matter. This matter does not spread in any direction beyond the town, over the fine plain which gently declines towards the bay of Naples. The volcanic eruption was so confined in its course or its fall, as to bury Pompeii, and only Pompeii:—for the showers of ashes and pumice-stone, which descended in the immediate neighbourhood, certainly made but a slight difference in the elevation of the plain. When a town has been buried by lava, like Herculaneum, the process is easily traced. You can follow the black, hardened lava from the cone of the mountain to the sea, whose waters it invaded for “many a rood;” and those who have seen the lava in its liquid state, when it flows on like a river of molten iron, can conceive at once how it would bury every thing it found in its way. There is often a confusion of ideas, among those who have not had the advantage of visiting these interesting places, as to the matter which covers Pompeii and Herculaneum. They fancy they were both buried by lava. Herculaneum was so, and the work of excavating there was like digging in a quarry of very hard stone. The descent into the places, cleared, is like the descent into a quarry or mine, and you are always under ground, lighted by torches. But Pompeii[122] was covered by loose mud, pumice-stone, and ashes; over which, in the course of centuries, there collected vegetable soil. Beneath this shallow soil, the whole is very crumbly and easy to dig,—in few spots more difficult than one of our common gravel-pits. The matter excavated is carried off in carts, and thrown outside the town; and at times when the labour is carried on with activity, as cart after cart withdraws with the earth that covered them, you see houses entire, except their roofs, which have nearly all fallen in, make their appearance; and, by degrees, a whole street opens to the sunshine or the shower, just like the streets of any inhabited neighbouring town. It is curious to observe, as the volcanic matter is removed, that the houses are built principally of lava, the more ancient product of the same Vesuvius, whose latter result buried and concealed Pompeii for so many ages.