He sprang off, and I saw no more of him.  A heavy Indian whip was fastened by a band to my wrist; I swung it into the air and lashed my horse’s flank with all the strength of my arm.  Away she darted, stretching close to the ground.  I could see nothing but a cloud of dust before me, but I knew that it concealed a band of many hundreds of buffalo.  In a moment I was in the midst of the cloud, half suffocated by the dust and stunned by the trampling of the flying herd; but I was drunk with the chase and cared for nothing but the buffalo.  Very soon a long dark mass became visible, looming through the dust; then I could distinguish each bulky carcass, the hoofs flying out beneath, the short tails held rigidly erect.  In a moment I was so close that I could have touched them with my gun.  Suddenly, to my utter amazement, the hoofs were jerked upward, the tails flourished in the air, and amid a cloud of dust the buffalo seemed to sink into the earth before me.  One vivid impression of that instant remains upon my mind.  I remember looking down upon the backs of several buffalo dimly visible through the dust.  We had run unawares upon a ravine.  At that moment I was not the most accurate judge of depth and width, but when I passed it on my return, I found it about twelve feet deep and not quite twice as wide at the bottom.  It was impossible to stop; I would have done so gladly if I could; so, half sliding, half plunging, down went the little mare.  I believe she came down on her knees in the loose sand at the bottom; I was pitched forward violently against her neck and nearly thrown over her head among the buffalo, who amid dust and confusion came tumbling in all around.  The mare was on her feet in an instant and scrambling like a cat up the opposite side.  I thought for a moment that she would have fallen back and crushed me, but with a violent effort she clambered out and gained the hard prairie above.  Glancing back I saw the huge head of a bull clinging as it were by the forefeet at the edge of the dusty gulf.  At length I was fairly among the buffalo.  They were less densely crowded than before, and I could see nothing but bulls, who always run at the rear of the herd.  As I passed amid them they would lower their heads, and turning as they ran, attempt to gore my horse; but as they were already at full speed there was no force in their onset, and as Pauline ran faster than they, they were always thrown behind her in the effort.  I soon began to distinguish cows amid the throng.  One just in front of me seemed to my liking, and I pushed close to her side.  Dropping the reins I fired, holding the muzzle of the gun within a foot of her shoulder.  Quick as lightning she sprang at Pauline; the little mare dodged the attack, and I lost sight of the wounded animal amid the tumultuous crowd.  Immediately after I selected another, and urging forward Pauline, shot into her both pistols in succession.  For a while I kept her in view, but in attempting to load my gun, lost sight of her