Then, all in a moment, and without any further warning, the blackness overhead was riven by the most appallingly vivid flash of lightning that I had ever seen, accompanied--not followed--by a crash of thunder that temporarily deafened all hands of us and caused the ship to quiver and tremble from stem to stern.  Then, while we were all standing agape, our ears deafened by the thunder and our eyes blinded by the glare of the lightning, a fierce gust of hot wind swept over us, filling our two staysails with a report like that of a cannon and laying the ship over to her sheer-strake.  Tasker, who was again officer of the watch, at once sprang to the wheel and assisted the helmsman to put it hard up; but almost before the ship had begun to gather way the first fierceness of the gust had passed, leaving us little more than a fresh breeze.  I therefore went aft and shouted to them--for they were as deaf as I was-- to bring the vessel up to her course again, when we began to move through the water at a speed of some five knots.