64 NORTHERN SWIFTS. 
river, at an average distance from it of nine miles. 
This part of it is quite or very nearly a dead level, 
and very little above the sea, densely timbered, 
and terminating at the spurs of the Cascade 
Mountains. Here the Sumass prairie and its lake, 
so often referred to, are situated. The lake is 
ten miles long, and about four-and-a-half wide. 
I have already explained how the prairie is 
flooded, and that in June the water again sub- 
sides; after this the growth of the various grasses 
and sedges (Cyperacee) is rapid beyond any- 
thing I have ever witnessed elsewhere. In two 
months the grass attains a height of four and 
seven feet. As the water disappears, swarms of 
insects accumulate, as if by magic ; birds of 
various species arrive to devour them, build 
their nests, and rear their young. 
Amongst the earliest of these visitors I noticed 
the Northern Swift (Nephocaetes Niger, Baird). 
It was a fogey day early in June, and, the insects 
being low, the birds were hovering close to the 
ground. I shot four. The next day I searched in 
vain, but never saw the birds again until the fall 
of the year, when they a second time made their 
appearance in large numbers—birds of the year 
as well as old ones. From their habit of flying at 
a great height, it is extremely difficult to obtain 
