18 
OENERALIA 
of an opinion by experts very difficult and accounts for the 
aversion or disdain that so often prevents a true conception 
of birds. 
All that is certain is that many species of birds that are 
of significance in the economy of Nature and of Man, are 
scarcely remarkable, because they are small and live an 
obscure life; yet there are crowds of them dispersed in the 
temperate zone of the E. Hemisphere, which sometimes, in 
consequence of certain meteorological phenomena, flock to- 
gether and may afford a conception of the mightiness of the 
work they represent and imply. 
Henry Gaetke, the celebrated German ornithologist,^ 
who for fifty years made observations of all birds that ap- 
peared in Helgoland or passed over that island, writes of the 
golden-crested wren, that is small and of even more delicate 
structure than the wren, that one autumn it appeared in 
enormous flocks: — of the flock itself the celebrated observer 
writes that for days and nights these crowds of tiny birds 
passed over the island in thick masses like the flakes in a 
heavy snowstorm ; those in need of rest literally covered the 
cliffs on the shore: there must have been millions. Under 
ordinary circumstances this little bird is a stay-at-home: and, 
though not at all common, it was still able to collect a flock 
of those dimensions. If we consider that this little bird, as 
far as we at present know, is exclusively an insect-eater 
doing its work with great diligence, we may form some con- 
ception of the dimensions and importance of the labour it 
performs. 
Before completing these introductory remarks mention 
must be made of the means of propagation of birds — con- 
^ „Der Vogelwart von Helgoland" ; „Die Vogelwarte Helgoland* : 
these have appeared in English too. 
