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‘P il > AVII, 4 
; Trans,, 1880, CLxx, 1 
1884] On the Evidence that the Earth’s Interior is Solid. 59I 
be subject to, by assuming as his premise that the carriages were 
rigidly attached to one another, 
Delaunay further objected to the precession and nutation theory 
of Hopkins and Thomson, on account of the slowness of the 
motion and the viscidity of the liquid interior, which would 
cause the earth to act as if it were a solid body.’ 
From observations made on the deflection of the plumb-line 
by the Himalaya mountains, Sir George B. Airy held, “that the 
whole of that country is floating upon a dense fluid, and that the 
thick mass of the lighter mountain-matter sinks deep in the fluid, 
and that the displacement of denser matter neutralizes almost en- 
tirely the attraction of the lofty mountains. The form of the 
‘arth is not such as would be taken by a solid structure, but such 
as wouid be taken by a fluid mass with solids floating upon it.’ 
In the case of Mr. Geo, H. Darwin's papers, it is difficult in 
` Some cases to understand exactly what he regards as the consti- 
tution of his assumed mathematical globes, and to express his 
ideas in non-mathematical language. His investigations appear 
=n made on the suppositions that the globe is a viscous non- 
elastic spheroid, an elastico-viscous one, and one either elastic, 
i€ or viscous. All these, if he is rightly understood, are 
considered to be homogeneous. Darwin then states that the 
Practical result of this paper may be summed up by saying 
that it is “strongly confirmatory of the view that the earth has a 
very great effective rigidity,” the term earth being substituted for 
the etical globes mathematically investigated by him.’4 
Paper he says that the word earth is used as an abbre- 
te = “a homogeneous rotating viscous spheroid.” ; 
$ ater paper “On the stresses due to the weight of conti- 
T he assumes that the earth is a homogeneous elastic 
Sphere, of which two conditions are possible, one that it is in- 
p pressible, the other that it is compressible. He then proceeds 
that in an earth thus constituted a state of stress must 
k wing to the inequalities between the continents and sea 
R Sag the discussion of this supposed condition, he says: 
that if th i t, then at a thou- 
— 8nd miles f, e earth be solid throughout, the 
: rom the surface the material must be as strong as 
ip 3 1872, V, 288 289 
Geol. M i 1868 > ¿ 
ete (1), v, so7—5r1, 
I—44. 
~35, 147-593. 
