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A blue ring that shows different shades of blue

The Cyanometer, and Antique device to Measure the Blue of the Sky


Despite a long quiescent period, an apparatus survives as a witness to the poetry of observing and measuring the sky’s blue.

We know that the sky’s intensity of blue varies according to factors like humidity, particles in the air and sunlight’s dispersion within the atmosphere. Far less well-known is that changes in altitude will transform and darken the blue of the sky. This fact puzzled and astonished Horace-Bénédict de Saussure, one of the fathers of modern mountaineering and meteorology. Saussure was also the inventor of the cyanometer, a device designed to measure the tones of blue of the celestial ceiling.

Obsessed with measuring meteorological phenomena through which his excursions into the mountains of Europe took him, Saussure (1740-1799) – a geologist, a meteorologist and a Swiss alpinist – invented and improved upon several scientific instruments. Among them were a magnetometer and the beautifully named diaphanometer for measuring the clarity of the atmosphere. In 1789, after years systematically recording tones of blue in the sky, Saussure developed his cyanometer, a simple circular device of 52 different shades of blue. These were presented on paper individually dyed by the meteorologist with a pigment evocatively called “Prussian Blue.” The circle begins at white and ends with black.

A ring with various shades of blue, held to to the sky

Saussure relied on his cyanometer for the rest of his life. The deepest blue he recorded was sighted from the top of Montblanc, and this measured some 39 degrees of blue on the scale of his precious device. Years later Alexander von Humboldt, another regular user of the cyanometer, recorded a blue sky of some 46 degrees from the top of the Chimborazo volcano in the Andes.

The cyanometer’s singular beauty is but further evidence of the power blue holds over the human mind, its emotionality and its art. The legendary Miles Davis’s obsession was with creating music defining everything blue in the world (in the groundbreaking album Kind of Blue) and the daring feat of artist, Yves Klein, included inventing and naming his own tone of blue. More recently, Slovenian artist Martin Bricelj Baraga, launched a spectacular project even titled Cyanometer. A monolithic work, it measures the tone of the celestial sphere, the quality of the air, and changes color to mimic the sky.

Upon its invention, the cyanometer rather quickly fell into disuse. After all, very little scientific information was given. That alone grants it poetic license. The beauty of the artifact – something like the melancholy in the blue of cyanotype algae – lies in the invitation to appreciate what, for all its subtlety, we seldom notice. It absorbs information from the space we inhabit, and leaves open the possibility of discovering universes both symbolic and emotional.


Images: Wikimedia Commons

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