Geology Reference
In-Depth Information
still cooling down from a time when it had originally been a
molten globe. Furthermore, he considered it was 'obvious' that
if the temperature at which rocks melted and the rate at which
they cooled down was known, then it should be possible to
calculate the time at which the Earth's crust had consolidated.
Recognising the di~culties in using what were essentially
unknown values for his calculation Kelvin initially allowed very
wide limits: 'I think we may with much probability say that the
consolidation cannot have taken place less than twenty million
years ago, or we should have more underground heat than we
actually have, nor more than four hundred million years ago, or
we should not have so much'. Given these very wide brackets
the intrusive impact of this physicist into the geological com-
munity, despite his rude comments, was initially quite small.
Four hundred million years for the age of the Earth was very
acceptable to most geologists at the time, and although twenty
million would be stretching things a bit, no-one took that very
seriously. But the subject continued to fascinate Kelvin. A few
years later, with some improved data to hand, he revised the
figures used in his original calculations, which brought the age
of the Earth down to a more definite one hundred million years.
Many geologists were less happy with this, but Kelvin backed
his arguments with all the authority that numbers and calcula-
tions could give him, and no one was better qualified to under-
stand the laws of thermodynamics. Not only that, his speech
propounding his new calculation was littered with more deroga-
tory remarks directed at geologists: 'A great reform in geologi-
cal speculation seems now to have become necessary'; 'It
[Hutton's Theory] is pervaded by confusion'; 'a complete mis-
interpretation of the physical laws'; 'it is quite certain that a
great mistake has been made', and so on. Although incensed by
this attack, most geologists were clearly intimidated by Kelvin's
authority with figures and felt obliged to heed his arguments.
While some like Darwin, who described Kelvin as his 'sorest
trouble', still clung to an intuitive belief that the Earth was much
