THE INCORPORATORS 161 
On his return to America in 1845, he spent two years in mis- 
sionary work in Pennsylvania, after which he was invited to assist 
Professor H. D. Rogers in Boston in preparing a map of 
Pennsylvania, showing the work of the first geological survey of 
the State. After a winter spent in Boston, Lesley was for three 
years pastor of a church in Milton, Massachusetts, at the end of 
which time, his religious views having undergone a change 
which made it impossible for him to remain a clergyman, he 
resigned his parish in May, 1852, and went to Philadelphia. 
Afterwards he was engaged for a period of about ten years in 
surveys of iron, coal and oil fields for the Pennsylvania Rail- 
road and other companies, as well as on his own account. During 
the summer of 1855, Lesley performed a notable piece of geolog- 
ical work, consisting of a survey of the Broad Top Mountain 
region of central Pennsylvania, which included a contour-line 
map of the semi-bituminous coal-field, “‘ with over eleven thou- 
sand stations levelled.” In 1856, he became Secretary of the 
American Iron Association, which necessitated his visiting all 
the iron works of the United States. He published at this time 
a large volume of statistics of the iron industries, also the “ Iron 
Manufacturers’ Guide,” and his “ Coal Manual.” 
In 1858 he was elected librarian of the American Philosophi- 
cal Society, which position he held for twenty-five years, giving 
much time and attention to the duties of the office. In 1860 he 
became interested in a process for the desulphurization of coal, 
but it was not financially successful, and he confined his energies 
thereafter to scientific and literary work. In 1862 and 1863 he 
was engaged in surveying at Glace Bay, on the coast of Cape 
Breton, and in the latter year made a trip to Europe to study the 
Bessemer steel process. 
During the season of 1865-66, Lesley delivered a course of 
lectures before the Lowell Institute in Boston, choosing for his 
subject “ Man’s Origin and Destiny.” 
Ill health again obliged him to desist from work, and he spent 
a year in Europe and a winter on the Nile. After his return, 
in 1869, he became editor of the United States Railroad and 
