After being a few days at sea the wind began to moderate, and finally died away; and instead thereof we had thunderstorms and waves, which, if not so big as mountains, would certainly have made pretty large hills. Many a night did we linger on deck till well nigh morning, entranced by the sublime beauty and terrible grandeur of those thunderstorms. The roar and rattle of heaven's artillery; the incessant _floods_ of lightning--crimson, blue, or white; our little craft hanging by the bows to the crest of each huge inky billow, or next moment buried in the valley of the waves, with a wall of black waters on every side; the wet deck, the slippery shrouds, and the faces of the men holding on to the ropes and appearing so strangely pale in the electric light; I see the whole picture even now as I write--a picture, indeed, that can never, never fade from my memory. Our cruising "ground" lay between the island and town of Mozambique in the south, to about Magadoxa, some seven or eight degrees north of the Equator. Nearly the whole of the slave-trade is carried on by the Arabs, one or two Spaniards sometimes engaging in it likewise. The slaves are brought from the far interior of South Africa, where they can be purchased for a small bag of rice each. They are taken down in chained gangs to the coast, and there in some secluded bay the dhows lie, waiting to take them on board and convey them to the slave-mart at Zanzibar, to which place Arab merchants come from the most distant parts of Arabia and Persia to buy them. Dhows are vessels with one or two masts, and a corresponding number of large sails, and of a very peculiar construction, being shaped somewhat like a short or Blucher boot, the high part of the boot representing the poop. They have a thatched roof over the deck, the projecting eaves of which render boarding exceedingly difficult to an enemy. Sometimes, on rounding the corner of a lagoon island, we would quietly and unexpectedly steam into the midst of a fleet of thirty to forty of these queer-looking vessels, very much to our own satisfaction, and their intense consternation. Imagine a cat popping down among as many mice, and you will be able to form some idea of the scramble that followed. However, by dint of steaming here and there, and expending a great deal of shot and shell, we generally managed to keep them together as a dog would a flock of sheep, until we examined all their papers with the aid of our interpreter, and probably picked out a prize.