The streets are generally about wide enough for one wagon, and how they do swarm with people! It is Broadway repeated in every street, in every court, in every alley! Such masses, such throngs, such multitudes of hurrying, bustling, struggling humanity! We never saw the like of it, hardly even in New York, I think. There are seldom any sidewalks, and when there are, they are not often wide enough to pass a man on without caroming on him. So everybody walks in the street--and where the street is wide enough, carriages are forever dashing along. Why a thousand people are not run over and crippled every day is a mystery that no man can solve. But if there is an eighth wonder in the world, it must be the dwelling-houses of Naples. I honestly believe a good majority of them are a hundred feet high! And the solid brick walls are seven feet through. You go up nine flights of stairs before you get to the "first" floor. No, not nine, but there or thereabouts. There is a little bird-cage of an iron railing in front of every window clear away up, up, up, among the eternal clouds, where the roof is, and there is always somebody looking out of every window--people of ordinary size looking out from the first floor, people a shade smaller from the second, people that look a little smaller yet from the third--and from thence upward they grow smaller and smaller by a regularly graduated diminution, till the folks in the topmost windows seem more like birds in an uncommonly tall martin-box than any thing else. The perspective of one of these narrow cracks of streets, with its rows of tall houses stretching away till they come together in the distance like railway tracks; its clothes-lines crossing over at all altitudes and waving their bannered raggedness over the swarms of people below; and the white-dressed women perched in balcony railings all the way from the pavement up to the heavens--a perspective like that is really worth going into Neapolitan details to see. ASCENT OF VESUVIUS--CONTINUED.