Gregory’s pillar

The article Gregory’s meridian line of 1673–1674: A St Andrews detective story by John Ceres Amson in the 2008 BSHM Bulletin tells how James Gregory, the first Regius Professor of Mathematics in the University of St Andrews, defined a meridian line in the 1670s with an accuracy of better than one part in 2000, an accuracy not surpassed for nearly a century.

This was the first secular meridian line in Europe. (Earlier meridian lines, mostly inside large churches, were used to establish the date of the Spring equinox so as to fix the date of Easter.)

Gregory was a very able mathematician, anticipating results of Newton and Leibniz on the calculus, and establishing the power series for sine, cosine and inverse tangent (though, as I told here, he was himself anticipated by the Keralan mathematician Madhavan (1340–1425)). Gregory’s time in St Andrews was not happy – as Dr Johnson noted somewhat later, the University was not a happy place at the time – and he left for Edinburgh after six years and died shortly afterwards.

Gregory's pillar

Gregory’s pillar, marking the southern end of his meridian line, is marked on the Ordnance Survey map, and stands in the back garden of a farm cottage on Scoonie Hill, a couple of kilometres south of St Andrews. Last weekend we walked that way on a beautiful Sunday afternoon, when I took the picture above.

However, as Amson points out, there is a mystery here: the pillar is not visible from the Old Library where Gregory had his observatory. (This is the case even without the complication of new buildings in St Andrews and the growth of trees on Scoonie Hill in the intervening centuries.) Amson speculates that the original wooden pillar was on the side of the hill in the middle of an agricultural field, and was moved to a safer location in the cottage garden when it was re-erected by David Gregory, James’ grand-nephew and fifth Regius professor, in 1757.

Amson ends his article with a plea for greater recognition for this extraordinary mathematician and astronomer, and celebration of his achievement. Wouldn’t the University’s 600th anniversary be a suitable time to do this?

About Peter Cameron

I count all the things that need to be counted.
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