The answer, when Maren found it, was disappointing in the way that true answers often are.
The column was a count of the ships that passed the point without signalling. Anton had been keeping a private tally of every vessel that ran dark past the light, because for two years he had been writing to a shipping authority that never wrote back, and he had wanted the letters to contain something other than complaint.
Seven hundred letters. One a morning. Each with a number in it.
Maren climbed the tower that evening, which she had promised herself she would stop doing, and stood at the rail while the automatic lamp went about its business without her.
Somewhere out past the point, a ship went by with no lights at all, and she found that she had already started counting.