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Thirdl}^, the experiments made by Hopkins upon metallic 
substances gave totally different results, and proved that the 
melting point of such bodies is not elevated by pressure : may 
it not be asked, therefore, how these results have been so com- 
pletely ignored, and upon what principle do the supporters of 
this hypothesis adopt conclusions drawn from experiments made 
upon a most unlikely class of bodies, to the exclusion of those 
upon substances which, as will be seen in the course of this 
enquiry, are most probably present in the earth’s interior in very 
large quantity ? 
h'ourthly and lastly, it may be mentioned that, long after the 
views of Bunsen and Hopkins, as regards the application of 
these, arguments to explaining the nature of the interior of the 
earth, were brought forward, we have the testimony of Mr. 
Fairbairn in 1861 that the later experiments on the effects of 
(much greater) pressures made by Mr. Hopkins and himself had 
caused that gentleman to greatly modify his opinions, and led 
him to the belief that it is only in the more compressible 
substances that the law holds true.” 
The above remarks will show how little reliance can be 
placed in arguments as to the entire solidity of the globe, based 
upon the effects of pressure in producing consolidation ; assum- 
ing, however, for argument’s sake, that the materials composing 
the earth’s mass do become more and more infusible according 
as they are situated nearer to its centre, it must still be remem- 
bered, on the other hand, that incontrovertible evidence has 
been produced by geologists to prove that the temperature or 
heat downwards from the surface also increases in direct ratio, 
and there is no sufficient proof in the results of Bunsen’s and 
Hopkins’s experiments to demonstrate that this augmentation 
in temperature would not more than counteract any tendency 
to solidity or increase of infusibility in the substances them- 
selves arising from the effect of pressure. 
The hypothesis that the earth was essentially solid necessitated 
that the phenomena of volcanoes should be explained upon the 
supposition that they had their sources in numerous small local 
basins scattered over the globe — a view which seems altogether 
incompatible with the results of chemical and mineralogical 
investigation, which proves that the ejected products are identical 
in constitution even if taken from the vents which are most 
distant from one another. 
The late researches of Professor Palmieri of Naples point out 
that distinct tidal phenomena can be recognised in the eruptions 
of Vesuvius : should these observations be confirmed, they must 
be considere<l as very strong evidence against any theory of 
volcanic action supposed to have its origin in mere local sources. 
The third hypothesis, which likens the earth to a gigantic 
