26 WILLIAM H. PICKERING 
fore go° from the central point. The latitude of this point is 25° S. 
Away from the center the tangential distances necessarily become 
more and more distorted, the distortion at the circumference making 
them appear = , or 1.6 times too large. 
: CONTINENTAL 
\ PLATEAU 
OCEANIC PLATEAU 
Figure 2 is taken from Gilbert’s Continental Problems of Geology 
(Smithsonian Report, 1892), p. 164, and is founded on the results of 
the Challenger Expedition as deduced by Murray. In it ordinates 
represent feet, and abscissas areas, the extreme abscissa representing 
the total area of the Earth’s surface. This area is composed chiefly 
of two plateaus: one the continental, whose mean altitude is 1,000 © 
feet above sea-level; the other the oceanic, whose mean altitude is 
= 14,000 feet. 
It will be noticed that the edge of the continental plateau is below 
sea-level, but not more than 1,000 feet below it. This contour 
may be taken, therefore, as the true boundary more properly than 
the water-line itself. In Fig. 1 it is indicated by a dotted line. Its 
position near the Antarctic continent is unknown. The location 
of the latter, excepting where indicated by the full line, has not been 
determined. The line composed of dashes therefore indicates its 
maximum possible area. : 
If we travel north go° from the central point of Fig. 1, to the 
immediate vicinity of Bering Strait, and erect another perpendicular, 
from which we again examine the globe, we shall obtain a view resem- 
