GEOLOGY. 701 



imminent death. Some seek a refuge and gather in groups 

 on the heights. Many are droAvned; others are attacked 

 and devoured by the crocodiles, which have now regained 

 all their vigour. A redoubtable eel, the Gymnotus elec- 

 tricus, adds to the dangers run by the mammals, the 

 shocks it gives being powerful enough to kill even horses.^ 



The aspect of the desert is more monotonous. With 

 the exception of the oases which it displays here and there 

 it is, in Africa, completely arid. In one of the deserts of 

 Upper Egyi^t, situated between the Nile and the Red Sea, 

 the eye only perceives an unbroken sheet of burning sand. 

 And yet upon its borders I found, to my great surprise, 

 braving the heat of the sun and never refreshed by a single 

 drop of water, numerous tufts of an asclepiad {Asdepias 

 procera ,Willd.) , the large, moist and velvety leaves of Avhich 

 glistened with freshness. It was an inexplicable problem ! 



But this last effort of life soon disappears, and Ave see 

 before us only an ocean of sand and a horizon of death. 

 Not a cry, not a murmur is heard, and scarce even a loiter- 

 ing vulture devours the last fragments of some camel which 

 has fallen on the sand, and the bleached skeleton of which 

 AviU soon be added to so many others now marking out 



' Humboldt says that it is not only the crocodiles and jaguars that lay snares 

 for the horse. This animal has also a formidable enemy among the fish. The 

 marshy waters of Bera and Eastro are filled with electric eels, the slimy bodies 

 of which, covered with yellow spots, spontaneously emit violent shocks in every 

 direction. These Gymnoti (the name they are known by in science) are five to six 

 feet long; they are strong enough to kill the most robust animals when they put 

 in action all their organs, armed as they are with an apparatus of numerous nerves, 

 at the same time and in a suitable direction. At TJritucu it had become necessary 

 to change the road across the steppe, owing to the eels having so increased in a 

 little river, that every year many horses, struck with paralysis, were drowned in 

 passing the ford. All the fish fly before the approach of these formidable eels. 

 They even assail unawares men fishing with a rod, the moistened line often form- 

 ing a medium for communicating the fatal shock. In this case the electric fluid 

 is discharged even from the bottom of the water. — Humboldt, Tableaux de la 

 Nature, t. i. p. 4.5. 



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