x PREFACE 
too, are often over-elaborate for those to whom 
ornithology is not the main business of life. Many 
people, however devoted to the subject, have not 
the time for the proper study of Dr. Gadow’s great 
work, which, moreover, being written in German, is 
a sealed book to numbers of English readers. For 
the study of bird anatomy they are often’ thrown 
back upon the good but insufficient treatises written 
for the use of medical students. Natural History 
books, describing the lives of birds, are many, and, 
not a few of them, first-rate, though, curiously, there 
was not, to my knowledge, any English book in 
which a general review of the known facts and of 
the problems of migration had been successfully un- 
dertaken, till the appearance of the second volume 
of Professor Newton’s Dictionary of Birds, containing 
a very able article on the subject. There are several 
books in English treating of flight. Of these 
Professor Marey’s Animal Mechanism seems to me 
the best. But some of his most instructive experi- 
ments have been made since its publication, and an 
account of them is to be found only in his later and 
larger work, Le Vol des O1seaux. It has been my 
wish to bring the work of the anatomist and physio- 
logist into connection with that of the student of 
flight and that of the outdoor naturalist. With this 
object I have made some investigations and observa- 
tions which, I believe, may lay claim to originality, 
and I have consulted the best English, French, and 
‘German books upon ornithology, as well as a number 
