Madam, - Mary Mulvihill writes that Archbishop James Ussher, in his efforts to calculate the age of the Earth, corresponded "with astronomers to learn how Newton's new mechanics affected calculations of the length of a year" (An Irishwoman's Diary, October 18th).
Ussher would have had to be exceptionally prescient to write about Newton's mechanics. When the Archbishop died in 1656 Isaac Newtown (born 1642) was still a schoolboy. - Yours, etc.,
COLIN ARMSTRONG,
Village Court,
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Newtownbreda Road,
Belfast.