PLACE OF ORIGIN OF THE MOON BT 
than the ocean bed, the specific gravity of the liquid in which they 
floated must have been 3.7. Later, when this liquid surface cooled, 
the huge depression thus formed was occupied by our present oceans. 
The volcanic islands in the oceans, such as Hawaii, were obviously 
formed after the withdrawal of the Moon, and are analogous to the 
small craters scattered over the lunar maria. While their surface 
material presents no extraordinary density, the lava being full of 
bubbles and small cavities, interesting results have been obtained 
by the Coast Survey with the pendulum. Observations were made 
by E. D. Preston near the summit, and on the slopes of Mauna 
Kea, Hawaii, at altitudes of 13,060, 6,660, and 8 feet. He writes: 
It appears that the lower half of Mauna Kea is of a very much greater density 
than the upper. The former gives a value of 3.7 and the latter 2.1, the mean 
density of the whole mountain being 2.9. ‘This is somewhat greater than that 
found for Haleakala [a neighboring volcano] and is notably larger than the 
density of the surface rocks. Indeed, this appears to be the highest value yet 
deduced from pendulum work. 
The remark of Major Dutton? is interesting in this connection, 
that a part of the bulk of these mountains is due to accumulation, 
and a part to uplifting. The upper half is clearly due to matter, 
chiefly scoria, which has been expelled from the various vents. ‘The 
lower half is probably due to the slow uplifting of the former ocean 
bed. 
It would seem as if borings carried on in this vicinity to a depth 
of only a few hundred feet would bring to the surface the same kind 
of rock material that, beneath the continents, would only be found at 
a depth of many miles. Presumably this material would turn out 
to be lava similar to that found on the surface, save that under the 
great pressure the innumerable little cavities, rendering the material 
generally so porous, would have practically disappeared. The fact 
that its density, 3.7, as determined by Preston, coincides with the 
theoretical value just deduced is of interest. 
Turning now to Fig. 4, six points indicated by circles have been 
marked along the coast-line of the eastern continent. Correspond- 
ing to these, six similar points have been marked along the American 
1 American Journal of Science, Vol. CXLV (1893), p. 256. 
2U. S. Geological Report, 1882-83, p. 195. 
