BIOGRAPHICAL SKCTCII OF ISAAC LEA, LL. D. LVII 



leyite, Lennilite, and Delmvarite, an aceouut of which Dr. Geuth, State 

 geologist, has given in his reports.* The two last-named he considers 

 are varieties of the same mineral. Dr. Lea was the first to discover that 

 interesting and rare mineral, Diaspore, in Pennsylvania. He fonnd it 

 on the farm of Mr. Lesley, and has the largest crystal on record, meas- 

 uring 4 inches in length. 



His intimacy with Admiral Wilkes made him acquainted with all the 

 proceedings of that remarkable expedition, and he frequently advised 

 with Dr. Lea in regard to the vast collection of natural history which 

 was made by the naturalists in charge. This friendship continued until 

 the death of the admiral. Dr. Lea has scores of loug and confidential 

 letters from him. 



When the late Dr. Bigsby, the eminent geologist, visited this country 

 about 1830, he passed the winter in Philadelphia and was a frequent 

 guest of Dr. Lea. Subsequently he was engaged in the i)ractice of medi- 

 cine for twenty years at a distance from London. Resigning his prac- 

 tice he engaged with enthusiasm in his favorite science, and produced 

 those elaborate works on geology which estnblished his reputation, and 

 his correspondence with Dr. Lea was-again renewed. The late J. Gwyu 

 Jeffreys was also a visitor at Dr. Lea's when in this country and spent 

 several days with him. He was the best conchologist of his time in 

 England, and distinguished for his writings on English mollusca. 



Dr. Lea was president of the Academy of Natural Sciences of Phila- 

 delphia from 1853 to 1858, and filled other official positions more than 

 half a century. He was vice-president of the American Philosophical 

 Society for several years, and was chairman of its two principal commit- 

 tees (publication and finance) until his second visit to Europe, when he 

 resigned the offices. 



In 1860 he presided at the meeting of the American Association for 

 the Advancement of Science, and five years afterwards, at Buffalo (there 

 being no meeting during the war of the rebellion), he retired in favor 

 of Dr. Gould, the astronomer, who was appointed to succeed him. 



Dr. Lea is one of the largest contributors to science in this country ; 

 he began publishing his papers in 1817, and the last contribution of im- 

 portance was issued in 187C, embracing a period of fifty-nine years of 

 active research. 



Although in his ninety-fourth year, he is blessed with good health, 

 and his mental and physical faculties continue unimpaired. His deep 

 interest in scientific matters was recently manifested by inviting the 

 members of the American Association for the Advancement of Science, 

 and their guests of the British Association at the nieeting in Philadel- 

 phia in September, 1884, to visit him at his summer residence at Long 

 Branch, where he had the pleasure of receiving and entertaining about 

 two hundred members. 



'Second Geological Survey of Pennsylvania, P, pp. 93 and 224. 



