156 SPARKS FROM A GEOLOGIST'S HAMMER. 



steppes of Russia and Siberia, like the prairies of the 

 Mississippi Valley, were once the bottom of comparatively 

 shallow seas or lakes. The tundras of northern Siberia 

 appear to have been inundated since the period of gen- 

 eral glaciation. This is also true of the polders along 

 the coast of the German Ocean. The Magyar puszta and 

 the regions of the tchornosjom or black earth of Russia 

 seem to have been produced by a former extension of the 

 waters of the Black Sea. The black earth or prairie re- 

 gion of southern Russia covers an area twice the size of 

 France. It appears that an obstructed outlet of the Black 

 Sea dammed the waters to such an altitude that the Black 

 and Caspian and Aral were one, a greater Mediterra- 

 nean spreading over the most fertile areas of the Orient, 

 which were thus preparing, as the Amei'ican prairies 

 were at the same time preparing, to become the garden 

 of the continent to which they belong. This lacustrine 

 region is the ancient Lectonia. In the progress of events 

 an earthquake-throe shivered the barriers of the Thracian 

 Bosphorus, and the Oriental prairie-land was drained. 

 The fable of the floating Symplegades perpetuates the 

 memory of the relative transpositions of land and water. 

 History preserves but an imperfect record of this gi-eat 

 hydrographic revolution. The story which tradition bore 

 down to the reach of history had grown vague and de- 

 fective. But tradition, which ever delights to reproduce 

 the marvels of the past, not only retained its hold upon 

 the great fact, but yielded to history some data which 

 have found a permanent record. Herodotus, the " father 

 of history," has supplied such geographical details as 

 enable us to trace the limits of land and water about 

 the northern shores of the Black Sea, as they existed sev- 



