Lesley. ] 60 [Jan. 20, 
1864, he became chief medical officer of the army in the Shenandoah val- 
ley, at Winchester, Va. May, 1865, he was breveted Lieutenant Colonel, 
and resigned his medical duties for work at the Smithsonian Institution. 
In 1865 he was elected Professor of Geology and Mineralogy in the Uni- 
versity of Pennsylvania, resigning his chair in 1872 on account of his 
western explorations; for, in 1866 he explored a second time the Bad 
Lands of Dakota, collecting largely vertebrate fossils for the Academy of 
Natural Sciences of Philadelphia. From 1867 to 1879, twelve years, he 
was United States Geologist in charge of the survey of the Territories. 
From 1879 to 1883 he was employed as Assistant Geologist of the United 
States Geological Survey in preparing for publication his surveys in the 
Territories. Relieved of this literary work in the Spring of 1883, he did 
field work in Montana until he resigned his position, in the Autumn of 
1886, his health having become so impaired that he was confined for the 
most of the time to his bed. He died December 22, 1887. 
Dr, Hayden never practiced medicine, but used his medical knowledge 
in the superintendence of the army hospitals. He received the title of 
LL.D, from the University of Rochester in 1876, and again from the Uni- 
versity of Pennsylvania in 1886. He was elected a member of the 
National Academy of Sciences in March, 1856; of the American Philo- 
sophical Society in July, 1860 ; and of many other societies in America and 
in Europe. 
His fame as a geologist in Europe was extraordinary. It is not too much 
to say that his name was more familiar to the geological world in Europe 
than that of any other American geologist. This was evident to those of 
his collaborators in the science who visited the foreign cities, or were in 
correspondence with foreign geologists. It was due to the exceptional 
number of his geological contributions, to the freshness of the fields which 
he explored, and to the untiring energy with which he published his 
observations as fast as they were made, and communicated them, in large 
editions, to all the working geologists abroad. The amount of Hayden 
literature (as it may be justly called) in every library of the world is sur- 
prisingly great. More than fifty octavo volumes, copiously illustrated 
with pictures, sections, topographical and colored maps, were published 
by him, to make known his territorial surveys from 1867 to 1879. His 
report on the Warren survey was published by the War Department; and 
in papers read before the Academy of Natural Sciences of Philadelphia, in 
1857 and 1858, and in the Transactions of the American Philosophical 
Society of Philadelphia, in 1862, describing not only the geology, but the 
living vertebrates, reptiles, fresh-water fish and shells of the region. 
Another paper in the Transactions of our Society (of the same date) made 
contributions to the ethnography and philology of the Indian tribes of the 
Missouri river. The same year he published a sketch of the Mandan 
language in the American Journal of Science ; and in 1869 notes on the 
Pawnee, Winnebago and Omaha languages in the Transactions of our 
Society. His second survey of the Bad Lands produced a memoir for the 
Academy of Natural Sciences of Philadelphia, in 1869. 
