Black rains fell at Slains, Scotland between 1863 and 1866, a total of eight in all. After two of these, writes Fort, “vast quantities of a substance described sometimes as ‘pumice stone,’ but sometimes as ‘slag,’ were washed upon the sea coast near Slains…Whatever it may have been the quantity of this substance was so enormous that, in Mr. Rust’s opinion [Rev. James Rust, Scottish Showers], to have produced so much of it would have required the united output of all the smelting works in the world.”
–Charles Fort, The Book of the Damned, p29-30 (The Complete Books of Charles Fort, Dover, c1974).