When I first heard of the cyanometer, I imagined a complicated machine with dials, cranks, and knobs. But what de Saussure actually “invented” was a cardboard chart with 53 cut-out squares sitting alongside 53 numbered swatches, or “nuances,” as he called them, of blue: you simply hold the sheet up to the sky and match its color, to the best of your ability, to a swatch. As in Humboldt’s Travels (Ross, 1852): “We beheld with admiration the azure colour of the sky. Its intensity at the zenith appeared to correspond to 41° of the cyanometer.” This latter sentence brings me great pleasure, but
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