198 PHYSICAL GEOGRAPHY OF THE SEA : 



general facts, to which our author might fitly have given the 

 priority suggested. First, the proportion of sea to land, de- 

 termined as being nearly three to one; or in other words, 

 three-fourths of the surface of the globe is actually covered 

 with water. Next, the fact (important in suggesting a disparity 

 in the physical forces which have acted on the two hemi- 

 spheres) of the great excess of land in the northern hemi- 

 sphere over that of the southern, being in the ratio of 1 1 to 

 4 ; on which condition depend the curious results that only 

 1-2 7th part of existing land has land diametrically opposite 

 to it in the other hemisphere, and that the line of the 

 equator, as it girdles the earth, rests on the ocean for five 

 sixths of its length. Another mode of estimating the pro- 

 portions and local relations of land and sea is obtained by 

 halving the globe longitudinally on the meridian of the 

 Canaries; when a much larger proportion of sea will be 

 found on the western half or hemisphere so defined, than on 

 the eastern. The main fact of the great predominance of 

 water on the surface of the globe being thus proved, and its 

 mean depth, as we shall see hereafter, approximately deter- 

 mined, we reach other conclusions of high interest to every 

 department of physical science. We shall notice only one 

 of these, in which geological theory, both past and pros- 

 pective, is more especially concerned. The mean elevation 

 above the sea level of all the land on the globe islands as 

 well as continents, mountains as well as plains is estimated 

 by Humboldt at somewhat less than 1,000 feet. The mean 

 depth of the great oceans of our planet is calculated by 

 Laplace, from the tides and other phenomena, to be at least 

 21,000 feet. Hence, allowing full margin for errors, the 

 entire submergence of the land might take place, leaving the 

 solid mass of the earth everywhere deeply covered with 

 waters an elliptical globe of ocean, moving still under the 

 influence of the same sublime laws which had before guided 

 its path through surrounding space. 



