78 BIOLOGICAL SOCIETY OF WASHINGTON. 



Still another pioneer was Dr. John Mitchell, born in England 

 about 1680 and settled, early in the last century, at Urbanna, 

 Virginia, where he remained nearly fifty years practising medi- 

 cine and promoting science. He appears to have been a man 

 of srenius and broad culture, and was one of the earliest chemists 

 and physicists in America. His political and botanical writings 

 were well received, and his map of North America is still an au- 

 thority in boundary matters. He was a correspondent of Lin- 

 naeus, and in 1740 sent Collinson a paper in which thirty new 

 genera of Virginia plants were proposed.* His Dissertation 

 upon the Elements of Botany and Zoology | was dated Vir- 

 ginia. 173S, and was thus almost contemporary with the first 

 edition of the Systema Natures- of Linnaeus, though it was not 

 printed until ten years after it was written. This was the first 

 work upon the principles of science ever written in America. In 

 1743 he communicated to the Royal Society an "Essay on the 

 Causes of the Different Colours of People in Different Climates," % 

 writing from the standpoint of an evolutionist. He also com- 

 municated an " Essay on the Properties and Uses of the Different 

 Kinds of Potash," § and a " Letter concerning the Force of 

 Electrical Cohesion." || His fame rests chiefly, however, upon 

 his investigations into the yellow fever epidemic of i737 — 4 3 ' 

 published after his death. % In 1743 he appears to have been en- 

 gaged in physiological researches upon the opossum, which, 

 however, were never published. In 1746 Dr. Mitchell returned 

 to England, and upon the voyage was captured by French or 

 Spanish pmxtes, and his collections, and apparently his manu- 

 scripts, destroyed. He became a Fellow of the Royal Society, 



♦Darlington, p. 21. 



t Dissertatio brevis de Principiis Botanicorum et Zoologorum, deque 

 novo stabiliendo natures rcrum Systcmati congruo, cum Appendicc aliquot 

 gene rum plantarum recens conditorum et in Virginia observatum. Nurem- 

 burg, 1748. 



J Phil. Trans., xliii, 1744. || Phil. Trans., 1. 



§ Phil. Trans., xlv. 1 Amer. Med. & Phil. Reg., iv. 



