MAURTS CHART. 9.1 



of its volcanoes ; Mount Opliir, directly opposite 

 Pichincha — then the Indian Ocean, the immense 

 plateau of Africa, the isle of St. Thomas, and the 

 Atlantic. In making this circuit, we are chiefly im- 

 pressed by the fact that the external surface of the 

 earth's crust is almost exactly represented by a 

 circle. It is not without difficulty that we represent 

 only a slightly undulating line, the inequalities 

 being exaggerated in order that they may be at all 

 perceptible. 



4. Northern Atlantic Ocean — Chart of Maury. 



» 



Tlie Atlantic Ocean takes the form of a great canal, 

 stretching directly from north to south, and trending 

 to the east in its northern part. With Maury's Chart 

 before us we shall find it comparatively easy to form 

 an idea of the configuration of this ocean-bed. 



The curves which indicate its varying level are 

 drawn at such a distance from each other as to mark 

 a thousand fathoms' difference in the relative depths. 

 Thus all the points situated between the shores and 

 the first curve vary in depth from to 1000 fathoms, 

 or GOOO feet ; all the points between the first curve 

 and the second augment in depth from 1000 to 2000 

 fathoms; those between the second and third from 

 2000 to 3000 fathoms ; and those between the thii'd 



