94° HOW HE IS MADE 
under water with perfect ease, and, more than 
that, they can, when they wish, sink slowly til 
nothing is left above water but their beaks, to 
breathe. And they can stay so as long as they 
choose, keeping still in one spot, without moving. 
A cormorant in a zodlogical garden, who 
wanted to catch some of the swallows skim- 
ming over the pond, sank his body till only his 
head was out, and held himself there perfectly 
still. 
Birds who are hunted, as geese, have been 
known to save their lives in that way, by sink- 
ing their body under water, leaving in sight only 
the tip of the bill, which is so small it is not 
readily seen. 
To do such things, birds must be able to make 
their bodies heavy when they choose, as well as 
light, which we know they are able to do by fill- 
ing their air-sacs and hollow bones with air. — 
There are many things still to be found out 
about the powers of birds. 

