GEOLOGY. C07 



But these healthful stations, scattei-ed over the sand, to 

 use the expression of Ptolemy, like the black spots on the 

 yellow hide of the panther, are sometimes large spaces, 

 abundantly supplied with springs and sheltered by a vigor- 

 ous vegetation. In the Sahara there are even some which 

 form small but populous kingdoms, and which the caravans 

 take several days to cross. 



When reviewing the steppes, those living deserts, other 

 pictures unfold themselves to our gaze. In them we see 

 diversity of vegetation sharply defined, so that we might 

 fancy each zone had at first its own special sheet of ver- 

 dure. As Humboldt says, " The history of the vegetable 

 envelope of our planet, and of its gradual propagation over 

 the naked svu-face of the earth, has its epochs, like the 

 most ancient history of the human race." 



In some places we find stepjoes Avhich display only an 

 attempt at vegetable life; extending over immense spaces 

 and losing themselves in a boundless horizon, they open out 

 before the eye like the ocean, but without offering the charm 

 of the perpetual movement of its waves. All is sadness. 



In other regions these great spaces, the surface of which 

 is only slightly irregular, are covered with a perfectly uni- 

 form vegetation ; one species rules there despotically and 

 stifles all the others. Such is the spectacle presented by 

 the Landes of Bordeaux, exclusively pervaded by heath, 

 which at the time of flowering waves gently like a sea 

 of purple, whose waves agitated by the breeze melt away 

 .in the azure of the distant horizon. 



Struck by the monotony of their steppes, thickly over- 

 grown by the humblest plants, the Jdongols named them 

 the land of grass. But it is particularly in America, where 

 they bear the name of pampas, that they dismay the tra- 

 veller by their immense extent and often by their im- 



