Michel-Eugene Chevreul was a French chemist who lived to be 103 (1786—1889). The Catholic Encyclopedia at New Advent* calls him a physicist, and philosopher, as well as chemist. His work on fats and fatty acids was so useful to the French soap and candle industries in the 19th century that he is one of the 72 French scientist that Gustave Eiffel placed around the Eiffel Tower. **

Chevreul moved onto color, and especially, color in great tapestries. He showed that the way we perceive color is dependent, not only on the color itself, but what was next to it. This article gives a quick overview of Chevreul and a picture of the Chevreul illusion. https://www.princeton.edu/~freshman/science/chevreul/ . 

The Chevreul illusion shows a series of strips laid out next to each other. They are all the same gray color but the strips change from lighter to darker hues. However, the eye perceives a change from dark to light, within each stripe of color, that is not really present.

Another discussion about the illusion is here https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3192777/  but if you don’t want to read the whole article, scroll down to Figure 2, where the author took a set of color stripes and embedded it twice in another field of changing color. It is difficult to believe that the two embedded sets are the same. But they are.

Diane Tucker’s article about Gustave Caillebotte mentions Chevreul and his effect on color in the French Impressionist painters. It’s a lovely read. https://theshymuseumgoer.com/2024/03/03/gustave-caillebotte-third-impressionist-exhibition-paintings 

*https://www.newadvent.org/cathen/03650b.htm

**https://en.wikipedia.org/wiki/List_of_the_72_names_on_the_Eiffel_Tower  

ALSO There is an eclipse on Monday. Here is a map. https://eclipse2024.org/eclipse_cities/statemap.php