64 Physical Geography as a Popular Study. 



in the two hemispheres is permanent. We have not read the 

 paper in which Mr. Yates put forward this ingenious specu- 

 lation, but we doubt there being sufficient evidence to raise 

 it above the level of a conjecture, and when we look to the 

 action of aqueous, igneous, and aerial causes of modification, 

 we are not disposed to attach very great importance to 

 a difference of average specific gravity, if it exist, in the land 

 of the two hemispheres, through a great metalliferous deposit 

 in one, and a more cavernous texture in the other. 



The great continental mass ranges from north-east to south- 

 east, thus crossing the earth's diurnal motion from west to east, 

 but what was the direction of former continents we do not 

 know ; it may at some periods have been widely different from 

 what it is now. 



Passing for the moment from the consideration of the 

 disposition of land and water masses as affecting climate, and 

 through that acting upon civilization, another important influ- 

 ence of such arrangements must be noticed, and that is the 

 facility they afford, or the difficulties they oppose to, inter- 

 communication and commerce. Hitherto lands much indented 

 by seas and navigable rivers have had an enormous advantage 

 in this respect over massive continents; and the advance of 

 Europe, as compared with Asia, has, in no small degree, been 

 occasioned by the extent and sinuosities of its coast lines. In 

 Europe there is a mile of coast for every hundred and eighty- 

 seven square miles of surface ; in Asia the proportion is one 

 mile of coast to five hundred and twenty-eight square miles of 

 surface ; in Africa one to seven hundred and thirty-eight ; in 

 North America one to two hundred and sixty-six; iu South 

 America one to three hundred and thirty. But we now live in 

 an epoch in which human invention modifies the value of these 

 conditions, great continents are being traversed by railways, 

 even before roads are constructed, and ultimately this may 

 more than compensate for their deficiency in coast. 



The physical characteristics of the different continents are 

 peculiarly interesting : — " Europe is, on the whole, a hilly 

 and mountainous country. Asia contains the loftiest mountain 

 groups of the globe, and also vast plateaux. Africa has its 

 lofty mountains and elevated plains. Deserts very little above 

 the sea level accompany the plateaux ; but are small in com- 

 parison. America, notwithstanding the important and lofty 

 chains of the Andes and Eocky Mountains, is mostly charac- 

 terized by its plains. The high lands are a fringe of plateaux, 

 and the gigantic valleys, of which those of the Mississippi, the 

 Amazons, and La Plata are examples, are low plains. Moun- 

 tains, except in the great chain of the Andes, in Central 

 America and on the west coast of the Andes, are subordinate, 



