Arthur, Maggie and Geo¬rey Holmes, in Durham c. 1930.
Today we know that the Whin Sill does indeed have a very
late Carboniferous age but its radiometric date is around
295 million years, as opposed to the 182 million years measured
by Paneth. Similarly, although the Cleveland dyke is indeed early
Tertiary, its radiometric age is about 60, not 26, million years.
The huge discrepancy in today's radiometric ages with Paneth's
helium results well illustrates not only how unreliable the
helium analyses were, but also how badly constrained the
geological ages of most igneous rocks were at that time. Like