Geology Reference
In-Depth Information
new machine. Great e¬orts were made to ensure that all the
equipment, built by hand, was free from contamination before
the new analyses were made. When the results came through,
as expected, there were the three lead isotopes already recog-
nised by Aston, but right at the end of the spectrum a tiny blip
could just be seen. Previously obscured by contamination, this
minute spectrum of 'ordinary' lead was finally visible in this
super-clean equipment, and identified itself as lead 204. The
missing piece in the uranium-lead jigsaw had at last been
found, twenty-five years after isotopes were first discovered.
Following these results, Nier wrote to Holmes whom he con-
sidered 'more than any other was central to ideas . . . in which
lead isotope studies of ores and rocks played a crucial role, [such
as] the construction of an absolute geologic time scale, ages of
oldest crust and minerals [and] the age of the Earth'. Nier asked
Holmes if he would like to collaborate on some analyses and, if
so, to send Nier some rocks. But in the same way that the young
Holmes had criticised Bertram Boltwood in print way back in
1911 for an omission in one of his papers, Nier had once sup-
ported critics of Holmes' theory on the origins of lead ore which,
it turned out, was based on some faulty data. Holmes thanked
Nier
'most cordially'
for sending him particulars of
'your most
important work'
, but despite the fact that Nier only needed
10 milligrams of lead for a complete analysis and that it was pos-
sible to analyse a sample every two days, something Holmes
must have dreamt of being able to do, Holmes replied:
'I have
no specimens that it would be worth while to send you at the
moment.'
A fit of pique perhaps? To be fair, Nier's letter did
arrive shortly before Maggie died when she must have been
gravely ill, so perhaps Holmes had other things on his mind at
the time.
It was to be another six years before Holmes needed some
data from Nier, whereupon a wonderful correspondence and
collaboration developed between them that resulted in a major
breakthrough for dating the age of the Earth. Unfortunately,
