JOURNAL 
: OF THE 
WASHINGTON ACADEMY OF SCIENCES 
Vou. 13 DEcEMBER 19, 1923 No. 21 
GEOPHYSICS.—The density of the Earth as calculated from the 
densities of Mauna Kea and Haleakala. Hinry 8. WASHINGTON, 
Geophysical Laboratory. . 
Of the various methods for determining the mean density of the 
Earth the oldest is that of measuring the attraction exerted by an 
isolated mountain. This was employed at Chimborazo by Bouguer 
as early as 1749, next at Schiehallion by Maskelyne and Hutton in 
1775, and later by others at other mountains.2. The method is open 
to very serious objections, as pointed out by Boys; difficulty in meas- 
uring the geometrical form and mass of the mountain, and ignorance 
or uncertainty as to the homogeneity or distribution in heterogeneity, 
the solidity of the mountain, and the character of the underlying 
crust of the Earth. This method, indeed, has been superseded by 
those based on laboratory experiment, such as with the torsion 
_ balance or the chemical balance. 
The last geodesist to use the ‘‘mountain observation” method for the 
determination of the mean density of the Earth (A) was E. D. Preston, 
of the U. 8. Coast and Geodetic Survey, in connection with pendulum 
and latitude observations at Mauna Kea on the Island of Hawaii’ 
in 1892. | 
In the course of a recent petrological study of the lavas of the Island 
of Hawaii I determined the specific gravities of the specimens that I 
analysed, including those of Mauna Kea,‘ and was struck with the 
discrepancies between my specific gravities and their average and 
those given by Preston, as well as the resulting values for the density 
of the Earth. 
1 Received Nov. 26, 1923. 
2 Cf. C. V. Boys in Glazebrook, A dictionary of applied physics, 3: 279. 1923. 
3K. D. Preston, U. 8. Coast and Geodetic Survey, Report for 1893, Appendix No. 12, 
pp. 625-634. 1894. 
4H.S. Washington, Amer. Journ. Sci. 5: 487-502. 1923; and Amer. Journ. Sci. 6: 361. 
1923. 
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