ABSTRACT
Scientific knowledge must be publicly communicated. The criterion for establishing the reality of a reported phenomenon is its observability by other people when the required conditions are reproduced. Newton achieved a very high scientific reputation very quickly. But despite being recognized for his great contributions, he became involved in a series of nasty quarrels with other scientists, disputing priority even when his own position was secure. Joseph Henry was the greatest American experimental scientist of the nineteenth century, but during his lifetime he was better known as an able administrator of the Smithsonian Institution. Henry's background was rather similar to that of his more famous contemporary. He came from a poor family received little schooling and went to work at an early age. The idea of natural selection had occurred to Wallace while he was on an expedition gathering specimens in Indonesia.
