MODERN SCIENTIFIC GEOGRAPHY. 717 



recent Tertiary strata. These same strata form the coast of Syrtis 

 Major, where yet the Mediterranean extends farthest southward, and 

 where probably was situated the last channel through which water 

 was supplied to the sea that once covered a portion of the Sahara. 

 That here gradual upheavals of the land have taken place, each up- 

 heaval succeeded by a protracted season of repose, is shown by the 

 terraces, the origin of which is so well known to the geologist. Ger- 

 hard Rohlfs found these terraces as he ascended the rising ground 

 back of Tolmita, the ancient Ptolemais. He observes that these ter- 

 races are separated from one another by levels several miles in width. 1 



But if, turning aside from these geological considerations, we again 

 glance at our map of relative depths, we almost everywhere find that 

 a flat coast accompanies a shallow sea; while, on the other hand, a 

 mountainous coast implies a sudden and precipitous inclination of the 

 neighboring sea-bottom. This would more plainly appear if our map 

 were on a larger scale, and had a greater number of depth-curves for 

 the purpose of comparison. This fact might be accounted for by 

 supposing that the comparatively sudden upheaval of the coast-hills 

 was connected with a considerable depression of the neighboring sea- 

 bottom, while the slow and periodic sinking of the flatter portions 

 gave rise to submarine terraces. But, aside from this hypothesis, the 

 representation of graduated submarine depths has a significance not 

 to be misunderstood in geological, zoological, and botanical investi- 

 gations. 



Turning now from the sea to the land, we find in our best modern 

 maps a number of figures indicating, as accurately as possible, the 

 elevations ; nay, even the attempt has been made, in the magnificent 

 atlas of Switzerland, to show the elevations by means of equidistant 

 curves. The Lehmann method of representing the surface of a coun- 

 try with equidistant level-lines would be, in many respects, of the 

 highest service for the study of the earth's surface, but as yet it can 

 be practically employed only in individual cases, partly from the want 

 of materials, partly also on account of technical difficulties. 



Cartography is a powerful aid to scientific geography, inasmuch 

 as it arranges in true projection a great mass of heterogeneous mate- 

 rials, bringing it before the eye within small space, and thus making 

 apparent relations which else could hardly be noticed. As for politi- 

 cal geography, viz., the description of the various empires of the 

 world, their area, provinces, population, etc., this we would regard 

 rather as a branch of statistics than of geography proper. Gaea. 



1 "Von Tripoli3 nach Alexandrien," 1. Bd., S. 169. 



