And to my immeasurable surprise the man calmly drew a pistol from his belt and levelled it across the table straight at my head.  I sprang to my feet with the idea of flinging myself upon and disarming him, for I could no longer doubt the fellow was stark, staring mad upon this one particular point; but before I could get at him the weapon exploded, and the ball, passing so close to my head that I felt it stir my hair, buried itself in the panelling of the cabin behind me.  With a savage snarl he raised his hand, and would have dashed the heavy pistol-butt in my face; but by that time I was upon him, and, seizing his throat with one hand, while I wrenched the weapon from his grasp with the other, I bore him to the deck, and planted my right knee square in the middle of his chest, pinning him securely down.