In 1784, German-born British astronomer William Herschel published an article about his observations of the Martian atmosphere in Philosophical Transactions and noted the occasional movement of a brighter region on Mars, which he attributed to clouds and vapors.[19][20] In 1809, French astronomer Honoré Flaugergues wrote about his observation of "yellow clouds" on Mars, which are likely to be dust storm events.[19] In 1864, William Rutter Dawes observed that "the ruddy tint of the planet does not arise from any peculiarity of its atmosphere; it seems to be fully proved by the fact that the redness is always deepest near the centre, where the atmosphere is thinnest."[21] Spectroscopic observations in the 1860s and 1870s[22] led many to think the atmosphere of Mars is similar to Earth's.