Publisher, geologist, paleontologist and conchologist, Lea prepared his first scientific paper for the Journal of the Academy of Natural Sciences of Philadelphia in 1818. Nearly 300 scientific articles appeared above his signature before 1876. He was President of the Academy from 1858-1863 and Dean of the Wistar Association from 1858-1863. He made two European trips with his family, to attend scientific gatherings, one in 1832, the other 1852-53. Much of this correspondence pertains to persons and places connected with the trips mentioned. Perhaps not a great collector himself, he exchanged and purchased large study groups which were described and figured by him. The great controversy with T. A. Conrad over priority of descriptions of fossil shells must be stressed in any discussion of Lea's scientific work, but little mention is made of this feud in the letters herein listed. His extensive cabinet and a small sustaining fund were donated to the U. S. National Museum.