CANVASS-BACK DUCK. 
221 
which is said to he a species of valisineria , grows on 
fresh water shoals of from seven to nine feet (but never 
where these are occasionally dry,) in long narrow grass- 
like blades of four or five feet in length ; the root is 
white,' and has some resemblance to small celery. This 
grass is in many places so thick, that a boat can with 
difficulty be rowed through it, it so impedes the oars. 
The shores are lined with large quantities of it, torn up 
by the ducks, and drifted up by the winds, lying like 
hay in wind rows. Wherever this plant grows in 
abundance, the canvass-backs may be expected, either 
to pay occasional visits, or to make it their regular 
residence during the winter. It occurs in some parts 
of the Hudson ; in the Delaware, near Gloucester, a 
few miles below Philadelphia ; and in most of the rivers 
that fall into the Chesapeake, to each of which particular 
places these ducks resort ; while in waters unprovided 
with this nutritive plant they are altogether unknown. 
On the first arrival of these birds in the Susquehannah, 
near Havre-de-Grace, they are generally lean ; but such 
is the abundance of their favourite food, that, towards 
the beginning of November, they are in pretty good 
order. They are excellent divers, and swim with great 
speed and agility. They sometimes assemble in such 
multitudes as to cover several acres of the river, and, 
when they rise suddenly, produce a noise resembling 
thunder. They float about these shoals, diving and 
tearing up the grass by the roots, which is the only 
part they eat. They are extremely shy, and can rarely 
be approached, unless by stratagem. When wounded 
in the wing, they dive to such prodigious distances, and 
with such rapidity, continuing it so perseveringly, and 
with such cunning and active vigour, as almost always 
to render the pursuit hopeless. From the great demand 
for these ducks, and the high price they uniformly bring 
in market, various modes are practised to get within 
gunshot of them. The most successful way is said to 
be, decoying them to the shore by means of a dog, while 
the gunner lies closely concealed in a proper situation. 
The dog, if properly trained, plays backwards and 
