De Saussure is credited with inventing the cyanometer in 1789. De Saussure's cyanometer had 53 sections, ranging from white to varying shades of blue (dyed with Prussian blue) and then to black, arranged in a circle; he used the device to measure the color of the sky at Geneva, Chamonix, and Mont Blanc. De Saussure concluded, correctly, that the color of the sky was dependent on the amount of particles suspended in the atmosphere. Humboldt was also an eager user of the cyanometer on his voyages and explorations in South America.