40 
REPORT— 184/. 
the hypothesis of the solid crust being as thin as here supposed, the pressure 
on the subjacent fluid cannot be less than the weight of the superincumbeut 
crust, in which case the fluid lava would necessarily rise into any free canal 
communicating with it, at least to the level of the surface of the ocean. 
Under such circumstances it would be impossible for any column of water 
to obtain access to the general imtss of the interior flui<l by open canaL«. To 
suppose it could do so by [lerc-olation through crevice's too minuU; to admit 
of fluid lava under enormous pressure being forced into them, and of being 
thus effectually closed, would seem to be too visionary to call for serious re¬ 
futation. I may also remark that the theory is altogether inconsistent, if I 
understand it correctly, with the fact of the surface of the fluid lava, in such 
volcanos as Slromboli and Kirauea, standing permanently at a great eleva¬ 
tion above the surface of the sea. 
In this theory it is assumed that the thickness of the earth’s solid crust is 
exceedingly small compared with the earth’s radius, and iu the reasoning by 
which this assumption is attempted to b<* justttii?d. pressure is assumed to 
have no influence iu promoting solhlification. On fhn* latter peiiol I trust we 
shall have before long bett»“r experimental evidence than we now possess: 
and as regards the assumption respecting the present thickness of the earth's 
crust, I shall hereafter explain iny reasons for considering it entirely untenable. 
The remaining theory which‘l have to discusn is that which professes to 
connect the existence of actual volcanos with the assumed original fluidity of 
the globe, but in(l|'peridently t>f any particular assumpfifm respecting tiie 
present thickness ol its solid crust, or the fluidity of its actual central nucleus. 
ut here our discussion must jissumo n far int)re general character than if it 
had reference merely to recent volcanos. J have In fact already intimated that 
the analogies between the plimnomena presented to us in nearly every district 
'’iolciit disturbance, and those which ate the 
jmmediate results of modern volcanic actinn. nm anoi. h.o* onlv 
suS m rVnr.-"* r-u ‘l'‘^refore to a further discussion of the 
noiiiena Thfar. 1 ^” " * »>ot be limitrif to ilic explunatioii of volcanic phff- 
for the rpasin * Ruj^csted to U8 certain hypotheses, wliirh, 
elevation I ^ for a ginoral theory of 
fluidity of the Proceed, therefore, on the hypothesis of the former 
the decree of tCi! t consequences deducible from it, 
vation,^andul Se pbmnom'ena established by obser- 
meutal hypothesis, and the thTo'^ foLded\'^oT7^^ ofourfunda- 
Section IT. On the Farm, Solidi/imtioyt and mckness of the Earth's Cntd. 
fluidity, the noi^'^ivhii^* ” adopting the hypothesis of the earth's foniier 
its surLe 7olCu " n is the/or;« which 
tual attractions of its comnonenl’ n^r /* motion and the mu- 
nected with this, is the law of Uw-f ^* 4 ’- point intimately con- 
a mass would arrange themselves If ^ t‘> which the particles of such 
lil>rium. These qu^^tions have hlluf U ^«ain astate ofequi- 
the results arrived at are as follow^ '"''‘'stigated by mathematicians; 
whosiaxiris*^tha\of surface will be that of an oblate spheroid 
(-■^O Al, tho»e poiu,. ^Lich ,1.0 donsh, i, ,h, ^ 
