"From some experiments made by me, of throwing water into the air and letting it come down in drops upon the plastic* surface, I became satisfied that the most perfect specimens of fossil rain drops must have been made by a slight shower, and not large rain drops. For where the rain falls thick and fast, and especially in large drops, it soon effaces the marks of separate drops, and produces irregular caveties with tortuous ridges . . . The finest examples of rain drops I have seen on mud were produced by the few scattered drops that fell after the principal shower had passed over, and prepared the mud to be finely impressed." Edward Hitchcock, Ichnology of New England, page 167
* By "plastic," he means soft or malleable, capable of being shaped.