One letter, carried to the edge / as Wilson drew the spots, 1769

The Wilson effect

Glasgow’s type founder, and what he saw at the edge

Where the mark sits

From centre

Depth

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The limb and the centre Where the letters would have been

Alexander Wilson was type founder to the University of Glasgow from 1748 and its first Regius Professor of Astronomy from 1760. In 1769 he noticed that sunspots look like saucer-shaped hollows as they near the edge of the Sun: the side nearest the centre disappears first. It is still called the Wilson effect. The man whose types this identity is reviving also wrote the law of how things look at the edge of a frame, so the mark can obey it: at the centre the letters are whole, and as they travel out they foreshorten by the cosine of the angle and their leading edge sinks out of sight. It gives the centre rule a Glasgow reason that owes nothing to cinema.

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