Blood Rain, a shower of grayish and reddish dust mingled with rain, which sometimes falls on vessels off the Atlantic coast of Africa and southern Europe. The dust of these showers has been ascertained by Ehrenberg to be largely made up of microscopic organisms, especially the silicious shells of diatoms; in a shower which fell at Lyons in 1846, he estimated the total weight at 720,000 lbs., of which one eighth, or 90,000 lbs., were these minute organisms. Figures of many of these may be seen in Dana's "Geology," under "Dynamical Geology." Darwin describes a shower near Cape Verd, which was at least 1,600 miles wide, covering an area of more than 1,000,000 square miles, and extending more than 1,000 miles from the coast of Africa. Lesser showers have fallen in Italy, reddish snow at the same time appearing on the Alps. The red color is owing to the presence of a red oxide of iron. One of the earliest of these showers is referred to in Homer's Iliad. The origin of the dust is not known; possibly it is extra-terrestrial. The species, of which over 300 have been made out, are not African; a few resemble South American. According to Dana, the zone in which these showers occur covers southern Europe and northern Africa, with the adjoining portion of the Atlantic, and corresponding latitudes in western and middle Asia.