NO. 8.| REMARKS ON THE EARTH’S CRUST. 73 
element of the surface of the inner nucleus as in the rest of the earth’s crust, 
or, what is almost the same thing, that these parts are also, on an average, 
in an equilibrium of pressure upon the inner nucleus. If this supposition is 
correct, we must be able to infer from it the peculiarity that appears to 
characterise the coast-stations, namely, that the gravity increases a little with 
an approach towards the coast-margin of the continents. It has been stated 
above that for 37 coast-stations on various continents, Hetmert found 
the difference between the observed and the normal acceleration to be 
0:00030 + 0:00005 m. 
According to Putnam, the coast-stations in North America along the Atlantic 
exhibit positive, or very small negative, differences, while the stations in the 
interior show much larger negative differences. ! 
The relative determinations made by the Austrian Navy during the years 
1892—1898, also always give positive differences at the coast-stations examined, 
these being situated on various continents — Australia, Asia, Africa and 
South America — along the Indian, Atlantic and Pacific Oceans. ? 
The incline of submarine parts of the continents towards the ocean depths 
outside differs in different places. It is generally somewhat less nearest land 
(about 1 in 250 for a distance of 50 km.), and increases farther out to 
about 1 in 100. The incline is steeper, however, at several places, e. g. 
along the west coast of North and South America, where it amounts to 
1 in 40.3 
If, as before, @ stands for the density in the firm mass under the oceans, 
and g, for that under the continents, we may imagine the crust of the earth 
to be formed of a sea, of depth h,, extending over the whole earth, and resting 
upon a shell of thickness (h, — h,) and a density @, when we add, as regards 
the continents, a mass of which the sum total is zero, but distributed in such a 
manner that above there will be a covering of thickness h, and density 
1 United States Coast and Geodetic Survey, Appendix No. 1. Report for 1894, p. 28. 
Relative determinations of gravity with half-seconds pendulums, and other pendulum 
imvestigations. G. R. Purnam. Washington, 1895. 
2 Relative Schwerebestimmungen durch Pendelbeobachtungen. Ausgefiihrt durch die 
k. und k. Kriegs-Marine in den Jahren 1892—1894. Herausgegeben yom k. und k. Reichs- 
Kriegs-Ministerium, Marine-Section. Vienna, 1895. 
Relative Schwerebestimmungen durch Pendelbeobachtungen, Heft Il. Verdffent- 
lichungen des hydrografischen Amtes der k. und k. Kriegs-Marine in Pola. Pola 1898. 
3 F. R. Hetmerr. Hoéhere Geoddsie Bad. Il, p. 345. 
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