A Cyanometer to Measure the Blueness of the Sky

This summer, the warmest in a long time, we have been particularly lucky in the number of blue sky days we've seen. Perhaps this is why this week's Most Loved post – a 1789 cyanometer for measuring the blueness of the sky, chosen by visual director for Stella McCartney, Jonathan Schofield– has been so joyfully received.

The cyanometer is attributed to Horace-Bénédict de Saussure and Alexander von Humboldt. Cyanome...