134 PROCEEDINGS OF THE AMERICAN ACADEMY 



Science, April, 1840, and Volume XL., April, 1841 ; a brief account 

 of the Aurora of May 29, 1840, contained in Volume XXXIX. of the 

 same journal for October, 1840; an account of the discovery of the 

 Comet of October 1, 1847, by his daughter, Miss Maria Mitchell, for 

 which she received the comet medal, offered by the King of Denmark, 

 also in the same journal, Volume V., N. S., for May, 1848. In Volume 

 IX. of the Second Series of the American Journal of Science, Mr. Mit- 

 chell has given a brief notice of the scientific tastes and attainments of 

 Walter Folger, of Nantucket. The theory which Mr. Mitchell sug- 

 gested, and skilfully defended, in regard to the tails of comets, asserted 

 that they "are formed by the sun's rays, slightly refracted by the 

 nucleus, in traversing the envelope of the comet, and uniting in an in- 

 finite number of points beyond it, throwing a stronger than ordinary 

 light on the ethereal medium, near to or more remote from the comet, 

 as the ray, from its relative position .and direction, is more or less re- 

 fracted." Later in life, he felt the difficulties of his own, as of all 

 other theories, on this perplexing subject. 



Charles Frederick Philip von Martius, the distinguished 

 botanist and traveller in Brazil, was born at Erlangen on the 17th of 

 April, 1794, and died at Munich, December 13, 1868. He came of a 

 learned stock: one of his ancestors, Galeottus Martius, born at Ra- 

 venna in 1428, was librarian of the celebrated library of Matthias 

 Corvinus, King of Hungary ; a great-uncle was the author of a Flora 

 of Moscow (the first edition of which, all but two copies, was consumed 

 in the conflagration of that city) ; and his father (who lived to a very 

 advanced age) was one of the three founders of the oldest botanical 

 Society extant, the Botanische Gesellschaft of Ratisbon. His botanical 

 teacher at the University of Erlangen was Schreber, who had studied 

 under Linnreus. His earliest work — his thesis for the doctorate — was 

 his Enumeratio Horti Botanici Erlangensis, in 1814. When, after the 

 death of Schreber, his collections were purchased for the Bavarian 

 Academy, the veteran Schrank was sent to Erlangen to convey them to 

 Munich. He there found in young Martius a student of such promise 

 that he attracted him to the Bavarian capital and employed him as his 

 assistant in the Botanic Garden. Here, while acting practically as 

 superintendent of the establishment, Martius was noticed by King 

 Maximilian, and soon after was selected by him to be one of the two 

 naturalists (Dr. Spix being the other) which that enlightened monarch 

 had insisted upon adding, at his own expense, to the scientific staff 



