100 
THE FOUNDATIONS OF THE EARTH. 
“’[Nature and Ait, April 1, 1807. 
together, and they become warm. A blacksmith 
beats a bar of iron with his hammer, and it 
becomes red hot. Why is tins'? We appeal to 
the “ mechanical theory,” and we are told in reply 
that — whenever motion (i. e. force) is arrested, the 
motion of the mass becomes transferred to the 
atoms or molecules composing it, and this molecular 
motion is heat. 
And now to apply this to our subject. In the 
collision, or condensation, or aggregation of the 
particles of matter that the nebular hypothesis 
affirms to have produced the various bodies of our 
system, an immense amount of motive power must 
have been arrested ; and inasmuch as this great store 
of force could not be lost or turned to nothing, it 
appeared as heat, and an intensity of heat was 
generated sufficient to reduce the whole mass to a 
state of fusion. To quote the words of one of the 
most famous exponents of this new philosophy — 
Dr. J. It. Mayer — “ Newton’s theory of gravitation, 
whilst it enables us to determine, from its present 
form, the earth’s state of aggregation in ages past, 
at the same time points out to us a source of heat 
powerful enough to produce such a state of 
aggregation, powerful enough to melt worlds ; it 
teaches us to consider the molten state of a planet 
as the result of the mechanical union of cosmical 
masses, and thus to derive the radiation of the sun 
and the heat in the bowels of the earth from a 
common origin.” And, as an example of the 
amount of heat this collision of cosmical masses 
would produce, Dr. Mayer cites that, supposing the 
earth to have been formed by the union of the two 
masses only, coming together from a great distance 
by the influence of their mutual attraction, the 
generated 'heat would ' have been sufficient, if the 
masses had been of nearly equal size, to raise the 
temperature of the whole body to from 3 0,000 to 
40,000 degrees of the centigrade scale — twenty 
times the temperature of the melting point of 
iron ; and the greater the number of parts thus 
brought into mechanical combination, the greater 
the quantity of heat that would be developed. 
“The form of the earth is its history ; ” and 
this form indicates with mathematical certainty 
that it was once a more or less fluid body ; the 
flattening at the poles being precisely of that 
extent which a liquid mass rotating at the speed of 
the earth would be subject to ; and the igneous 
phenomena of the earth’s crust, and the store of 
heat yet embowelled in its interior, are ample evi- 
dence that its former fluid condition was that of a 
molten mass rather than that of an aqueous 
solution. 
But, assuming this to have been the origin of the 
primary condition of the earth, there must have 
been a time when the igneous body began to part 
with its heat, by radiation into surrounding space ; 
and it is in this cooling process that we are to look 
for a cause for the diversity of geological features 
that the surface of our planet presents to view. 
We may reasonably suppose, and the heated 
state of the earth’s interior supports the sup- 
position, that the first portion of the globe to cool 
was the exterior. The cooling and solidification of 
this portion would result in the production of a 
solid shell enclosing a molten nucleus, somewhat as 
we now find to be the case. Now between this 
solid shell and molten interior there would be a 
constant succession of conflicting actions : the 
shell, contracting as it cooled, would squeeze up, as 
it were, the interior : the interior, in its turn 
solidifying, would expand — for all substances expand 
in passing from the molten to the solid state — and 
thrust outward the confining shell ; then, contracting 
as it further cooled, it would shrink away from the 
shell which, now unsupported, would fall in upon 
the retreating nucleus. By actions like these, the 
smooth surface which the planet might otherwise 
have retained would be broken up and distorted ; 
mountain ranges would be formed by the ejection 
of the molten interior through the broken shell ; 
continents be jwoduced by the alternate thrustings- 
out and fallings-in which the shell would be subject 
to ; and all those irregularities be occasioned which 
manifest themselves in the igneous foundations of 
the globe. 
Fire on the one hand, and water on the other, are 
the two elements to which all the geological 
features of the earth are referable. With the 
second of these elements we have no concern in 
this sketch, for it is tolerably well known that its 
action pi’oduced those deposits which constitute the 
secondary and tertiary formations of the geologist, 
and which we may regard as superstructures reared 
iqion a foundation that had a fiery origin. In- 
credible as it may appear to those who look at the 
present condition of the world they inhabit, there 
can be little doubt that that world was once a fiery 
globe, glowing possibly with a fervour comparable 
with that of the sun as we now behold it, though of 
far less significant size. How many centuries — how 
many hundred centuries — have elapsed since this 
was the case ? We have an approximation to the 
period, but it may be enormously in error. Sir 
William Thompson, from a calculation of the rate 
of cooling of earthly bodies, assigns for the cooling 
of the crust of the earth, from a state of fusion to 
its present temperature, a period of 98 millions of 
years. And if this incomprehensible interval has 
elapsed since the earth took its finite form, how 
great, how stupendous, must be the lapse of time 
that has intervened since the matter of which it is 
composed, wandered through space a chaotic mass 
“ without form and void \ ” 
