60 THE MAMMOTH. 



the world, the Yenesei having a course of two thousand 

 five hundred miles, and the Lena of two thousand miles. 

 These rivers are filled with running water in their upper 

 course, when frozen over at their mouths for several hun- 

 dred miles, where they remain blocked with ice during 

 one-half the year. This causes great floods ; for the water 

 finding no open channel rushes over the ice and sweeps 

 along forests and great quantities of soil and gravel mixed 

 with ice. 



The missionary Hue, in his "Travels in Thibet," in 1846, 

 relates that after many of his party had been frozen to 

 death, the survivors pitched their tent on the banks of the 

 Mouroui-Ousson, and from their encampment saw some 

 black, shapeless objects ranged in file across the stream. 

 On drawing near these objects were discovered to be a 

 troop of about fifty wild oxen, called Yak by the Thibetans, 

 encrusted in ice. They probably had tried to swim across 

 the stream at the moment of congelation, and were unable 

 to disengage themselves. Their heads, surmounted by 

 huge horns, were still above the surface, and their bodies 

 could be seen in the ice as though they were still in the 

 act of swimming. So it may be inferred that mammoths, 

 in returning from their pastures, were caught while cross- 

 ing the streams by the sudden congealing of the water. 

 Others, of course, died by various means, natural or other- 

 wise, in the northern regions, perhaps not infrequently by 

 the water breaking through great barriers, and in devas- 

 tating the country, carrying the luckless mammoth into the 

 Frozen Ocean. This view will not account for the entire 

 destruction of the animal. It may be that a gradual 

 change in the climate, and the consequent diminution 

 of food, had something to do with its final extinction. 

 This will not, however, account for the final disappearance 

 in Europe and America. Whether Siberia was its last 

 retreat, and from Europe and America it gradually with- 



