162 NATIONAL ACADEMY OF SCIENCES 
Mining Register, and from that time until 1872 was engaged 
chiefly in surveys in the South. In the latter year he was 
appointed Professor of Geology in the School of Mines of the 
University of Pennsylvania. In the organization of the Towne 
Scientific School Professor Lesley took great delight and gave 
much time and thought to his teaching, which was always a 
favorite work, and aroused enthusiasm in his pupils. 
The crowning event of his life was, however, his appointment 
to the office of State Geologist of Pennsylvania, which occurred 
in 1874. The second Geological Survey of Pennsylvania was an 
undertaking of great magnitude and extended over a period of 
20 years. Lesley organized it with much care, and had as his 
assistants Frazer, Stevenson, Prince, Chance, D’Invilliers, Genth, 
and many other geologists and chemists. To the publication of 
results he gave the closest personal attention. His system was 
to publish numerous “ reports of progress,” each containing all 
the data relating to a single district or county. More than a 
hundred such volumes were issued, and at the end a final report 
summarizing the whole. He had nearly finished this latter work 
when in 1893 his health gave way completely, and he was obliged 
to desist. Sir Archibald Geikie said of the survey in a letter 
written at this time “ It is in my opinion a monument of patient 
skill, thoughtfully organized, sympathetically carried on, and 
admirably co-ordinated, through all its branches and all its prog- 
ress. I think it will be of the utmost value industrially to the 
State of Pennsylvania.” 
Lesley remained some years in Philadelphia, and afterwards 
returned once more to Milton, Massachusetts, where he died in 
June, 1903. 
(From Mary Lrstrey Ames, “ Life and Letters of Peter and Susan Lesley,” 
1909.) 
MIERS FISHER LONGSTRETH 
Born, March 15, 1819; died, December 27, 1891 
Longstreth was born in Philadelphia in 1819. He was edu- 
cated in the schools of the Society of Friends, and his early life 
was spent asa merchant. He devoted his leisure hours, however, 
