Xxiv HISTORICAL PREFACE. 
Lawrence were continuing their studies and writings, and many other names of lesser 
note were contributing their several shares to the whole result: the figure of John Cassin 
stands prominent. Cassin was born September 6, 1813, and passed from view in the 
Quaker City, January 10, 1869. Numerous valuable papers and several important works 
attest the assiduity and success with which he cultivated his favorite science to the end 
of his days. I think that his first paper was the description of a new hawk, Cymindis 
wilsont, in 1847. Among his most important works are the Ornithology of the Wilkes 
Exploring Expedition ; of the Perry Japan Expedition ; and of the Gilliss Expedition to 
Chili. Aside from his strong codperation with Baird in the great work to be presently 
noticed, Cassin’s seal is set upon North American ornithology in the beautiful book 
begun in 1853 and finished in 1856, entitled “Ilustrations of the Birds of California,” 
etc., forming a large octavo volume, illustrated with fifty colored plates. His distinc 
tive place in ornithology is this: he was the only ornithologist this country has ever 
produced who was as familiar with the birds of the Old World as with those of America. 
Enjoying the facilities of the then unrivalled collection of the Philadelphia Academy, his 
monographic studies were pushed into almost every group of birds of the world at 
large. He was patient and laborious in the technic of his art, and full of book-learning 
in the history of his subject ; with the result, that the Cassinian period, largely by the 
work of Cassin himself, is marked by its “bookishness,” by its breadth and scope in 
ornithology at large, and by the first decided change since Audubon in the aspect of the 
classification and nomenclature of the birds of our country. The Cassinian period marks 
the culmination of the changes that wrought the fall of the Audubonian sceptre in all 
that relates to the technicalities of the science, and consequently represents the beginning 
of a new epoch. 
The peers of this period are only three, — Lawrence, Brewer, and Baird. The for- 
mer of these, already an eminent ornithologist, continued his rapidly succeeding . papers 
and was preparing his share of Baird’s great work of 1858; though later his attention be- 
came so closely fixed upon the birds of Central and South America, that a “ Lawrencian , 
period” is to be found in the history of the ornithology of those countries rather than 
of our own. Dr. Brewer’s various articles appeared, and in 1857 this author, so well 
known since Audubonian times, became the recognized leading odlogist of North America, 
through the publication of the first part of his “ North American Odlogy ” — a work unfor- 
tunately suspended at this point. Though thus fragmentary, this quarto volume stands 
as the first systematic treatise published in this country exclusively devoted to odlogy, and 
giving a considerable series of colored illustrations of eggs. “But a larger measure of the 
world’s regard became his much later, when, in 1874, appeared the great “ History of North 
American Birds,” in three quarto volumes, all the biographical matter of which was by 
him ; and, even as I write, two more volumes are about to appear, in which: he has like 
large share. Thus closely is the name of Brewer identified with the progress of the 
science for nearly half a century, — from 1837 at least, to 1884, some four years after his 
death, which occurred January 23, 1880. He was born in Boston, November 21, 1814. 
Baird published little during the Cassinian period, being then intent upon the great 
work about to appear ; but the number of workers in special fields attests the activity 
of the times. S. W. Woodhouse published his completed observations upon the birds 
of the Southwest in an illustrated octavo volume. Zadock Thompson’s “ Natural History 
