I was handing him his gun when one of our native boatmen, laughing at our fright, made signs that there was no danger, and seizing a piece of drift-wood floating by, adroitly threw it across its mouth.  The vast jaw of the monster came crashing down on it.  There they stuck, and the native assured us, through Pedro, that he was now quite harmless. McRitchie took a steady aim at the creature's eye, while a native stood ready with a coil of ropes to throw over it directly it was killed, or it would have sunk, I fancy, out of sight in an instant.  McRitchie's bullet took immediate effect, and we soon had the creature hauled up on the nearest bank, where our medico had the opportunity of anatomically examining him at his leisure.  While he was thus employed, Gerard and I agreed that it would be a good opportunity to prepare dinner, assisted by Pedro.  The natives preferred sleeping in their canoe.  While we were engaged over our fish, I on a sudden looked up, and saw a huge animal of the tiger species stealing catlike towards the doctor, attracted probably by the carcass of the alligator.  The creature seemed at that moment about to make its fatal spring.  I had my gun providentially by my side.  I shrieked out to the doctor to be on his guard, and at the same moment raised my weapon to my shoulder to fire.  He had the large knife with which he had been cutting up the alligator in his hand. Resting on my knee, I fired, and though I did not flatter myself that I was a good shot, happily hit the animal on the head.  He fell backwards, stunned but not dead; and the doctor, rushing forward with his knife, deprived the creature of existence, thanking me in the same breath for the service I had rendered him.