THE NATURE OP THE INTERIOR OP THE EARTH. 
125 
but which further proved, experimentally, that a sphere filled 
with liquid matter would, under the circumstances, behave in 
precisely similar manner as an entirely solid one ; and, conse- 
quently, that the fact of the earth being either solid or liquid in 
its interior could not only have no influence whatever on the 
rates of precession and nutation, but could not be used as a 
means of deciding anything as to the real thickness of the 
earth’s crust. 
The astronomical arguments in favour of a solid, or nearly 
solid, globe being thus altogether invalidated, it remains to 
enquire as to whether any other facts can be advanced in support 
of this hypothesis. 
In 1849 Professor J. Thomson announced, from theoretical 
considerations, that the fusing points of bodies must become 
elevated when subjected to pressure, or, in other words, that 
under the influence of pressure bodies would require more heat 
to melt them or keep them in the molten condition ; a view which 
was, in 1850, confirmed by Bunsen’s experiments on spermaceti 
and paraffine, and still further corroborated, in 1854, by the 
more complete experiments of Hopkins on these bodies, as well 
as on wax and sulphur. 
Keasoning upon these facts as a basis, Bunsen argued that the 
earth could not be other than solid to the core, since the 
enormous pressure accumulated at its centre would cause its % 
internal substance to become so infusible that it could not 
remain in the molten state ; and this opinion was adopted by 
Hopkins, as confirming the conclusions which, as before men- 
tioned, he imagined had been proved by astronomical deductions. 
If we now enquire into the value of these data, we will also 
find that they are not entitled to much confidence. 
In the first place it is assuming that our earth is made up of 
substances like the wax, spermaceti, paraffine or sulphur ex- 
perimented upon by Bunsen and Hopkins, and which are in 
nature about as diametrically opposite to what we know the 
earth must be composed of, as could well be selected for com- 
parison. 
Secondly, on examining into the details of the experimental 
results, it appears, that although the melting points of these 
bodies undoubtedly became higher under the influence of pres- 
sure, that the ratio of their so doing did not continue the same 
in proportion as the pressure was augmented, but on the con- 
trary diminished after a certain point was reached, thus leading 
to the inference drawn some time back by the author of this 
communication, that bodies after attaining their point of 
maximum density may not become more infusible by increased 
pressure, but, on the contrary, may possibly become even more 
fusible as the pressure is still further augmented. 
