30 WILLIAM H. PICKERING 
in the vicinity of the central meridian, which is the portion of the 
map to which we shall especially refer. ‘The shaded areas represent 
those parts of the ocean that are more than 1,000 feet in depth. 
Regarding the unshaded area between America and Asia we have 
no information. 
When the Earth-Moon planet condensed from the original nebula, 
its denser materials collected at the lower levels, while the lighter 
ones were distributed with considerable uniformity over its surface. 
At the present day we find the lighter materials missing from one 
hemisphere. ‘The mean surface density of the continents is about 
2.7. ‘Their mean density is certainly greater. We find a large mass 
of material now up in the sky, which it is generally believed by astron- 
omers formerly formed part of our Earth, and the density of this 
material, after some compression by its own gravity, we find to be 
3.4, or not far from that of the missing continents. From this we 
conclude that this mass of material formerly covered that part of 
the Earth where the continents are lacking, and which is now occupied 
by the Pacific Ocean. In fact, there is no other place from which 
it could have come. 
Who it was that first suggested that the Moon originated in the 
Pacific is unknown. The idea seems to be a very old one. The 
object of the present paper is to find what support for this hypothesis 
is afforded by the results of modern science, when examined both 
qualitatively and quantitatively. 
The volume of the Moon is equivalent to a solid whose surface is 
equal to that of all our terrestrial oceans, and whose depth is thirty- 
six miles. It seems probable, therefore, that at this time the Earth 
had a solid crust averaging thirty-six miles in thickness, beneath 
which the temperature was so high that the materials were in places 
liquid, and in other places only kept solid by the enormous pressure 
of the superincumbent material. When the Moon separated from 
us, three-quarters of this crust was carried away, and it is suggested 
that the remainder was torn in two to form the eastern and western 
continents. These then floated on the liquid surface like two large 
ice-floes. 
If their specific gravity was the same as that of the Moon, 3.4, 
since the continental plateau averages nearly three miles higher 
