RAPACIOUS BIRDS HIS “FIRST WORK” 87 
explained by him in the preface to the first volume 
as follows :—“ The object I had in view when, 
many years ago, I commenced the observations 
recorded in this work was at some convenient 
season to lay before the public descriptions of the 
birds of Great Britain, more extended, and if 
possible more correct, than any previously offered ; ” 
and in the preface to the Rapacious Birds , he says : 
“Ornithology can be successfully prosecuted only 
by examining the internal structure, the external 
form, the actions and habits, the distribution and 
the various relations of the objects to which it 
refers ; ” adding, “ all arrangements of birds hitherto 
published are merely artificial, inasmuch as in their 
details reference is had only to one or a few sets of 
organs.” He further says he had not written 
without full preparation, having been at work for 
twenty years accumulating facts by his own 
observations in many fields, by numerous com¬ 
munications with other observers, by examination 
of many specimens, in museums and in his own 
possession, derived from various parts of the world, 
and by dissection of such birds as were available to 
him. 
The publication of the three volumes of the 
History of British Birds formed the commencement 
of a new era in ornithology, and the result was to 
revolutionise ~ to a great extent that branch of 
natural science. It was in accordance with the 
principles indicated in the above quotations that 
the book was written, and its value from a 
