VOl 1906 in ] Deane > Letters of J. J. Audubon and S. F. Baird. 195 



tween 1840 and 1846, show a growing friendship between their 

 authors. 



Baird made his first visit to Audubon in New York in February, 

 1842, and in November of the same year Audubon wrote an urgent 

 letter to his young friend, inviting him to accompany him on his 

 proposed trip to the Missouri River, and offering him most liberal 

 inducements. During these years Baird was furnishing Audubon 

 with much valuable material in both birds and quadrupeds. Some 

 of the birds which he collected in and about Carlisle, Pa., and which 

 are referred to in these early letters, are to-day in the Baird brothers 

 collection in the Smithsonian Institution. This collection num- 

 bered over 3000 skins and formed the basis of the present National 

 Museum collection. 



The two species of Tyfanula, the subject of their first ornitho- 

 logical paper, are probably mentioned in these letters for the first 

 time. A letter from Mr. Witmer Stone, relative to other corre- 

 spondence on the subject of these flycatchers, to which he has had 

 access, is so complete and to the point, that I quote in full. 



"The little Flycatchers mentioned in the following letters, whose 

 identity caused so much speculation on the part of the young orni- 

 thologists of Carlisle, are now placed in the genus Empidonax, one 

 of the most perplexing groups of North American birds. 



"There occur in Pennsylvania four distinct species. (1) E. 

 virescens, first clearly distinguished by Vieillot, and almost simul- 

 taneously by Wilson, but subsequently for many years known by 

 the name acadicus Gmelin, of very doubtful application. (2) E. 

 trailli, first described by Audubon (our eastern race is E. trailli 

 alnorum). (3) E. flaviventris, the bird described by Baird in the 

 letter to Audubon, dated June 4, 1840, and later published under 

 the above name. (4) E. minimus, the bird described briefly in the 

 letter to Audubon dated June 21, 1841, and compared with acadicus, 

 and finally published along with the other in the first volume of the 

 'Proceedings' of the Academy of Natural Sciences of Philadelphia, 

 by the brothers Baird; this paper being Spencer Baird's first con- 

 tribution to science. 



"Swainson and Richardson had published a species of this same 

 group Under the name pusilla, with which the Bairds vainly endea- 

 vored to identify one or the other of their new species without 



