328 
WILD NORWAY. 
this catch, curiously enough, being destined for trans- 
Atlantic markets. 
A great phenomenon, of which one may often enjoy 
opportunities at sea for observation, is that of migration. 
The transit over wide oceans of puny creatures, such 
as birds and insects, is so extraordinary, its character 
still so mysterious and imperfectly understood in detail, 
as to render every record interesting, and some valuable. 
The following notes on this subject include observations 
made during twenty-four voyages by my brothers and 
myself across the North Sea. 
To begin with the sea-birds — as every voyager 
knows, one sees gulls in mid-ocean at all seasons, and 
it is difficult to deduce any conclusions from their 
desultory flight. In May and June the Gulls seen are 
exclusively immature—young Kittiwakes with black- 
tipped tails, and other Gulls in that duskier plumage 
indicative of the second or third of the four years which 
nature has assigned as the period of adolescence in the 
Laridse. The adults at that season are, of course, 
engaged at their breeding-stations, and it is, perhaps, 
worthy of remark that few Gulls will be seen in mid-sea 
during the last two or three hours before dark. 
Similarly with the rock-fowl—Guillemots, Puffins, 
and the like. These, by the middle of May, have drawn 
landwards, and during the rest of that month and June 
no sea-birds (save the gulls aforesaid) will be seen far 
out. But in July the Guillemots, Razorbills, and 
Puffins, with a few stray Gannets (mostly immature), 
return to their pelagic haunts, while gulls, old and 
young, populate the middle seas. 
Thus, on July 12th, I have notes of all the species 
