Weber-Fechner law introduced. Describing the relationship between physical stimuli and human perception as logarithmic, it was one of the first mathematical models in the field of human cognition. Weber and Fechner were early German experimental psychologists.
Number theorist Nathan Fine born in Philadelphia, Pennsylvania. He is responsible for the couplet, "Chebychev said it, and I'll say it again. / There's always a prime between N and 2N," which he composed for Paul Erdos, according to the source below.