It was a very easy and comfortable way to get a bite of breakfast, while waiting for her baby to finish nursing.

And every little while, from the big blowhole or nostril on top of her head she would 'spout,' or send up a spray-like jet of steamy breath.

And every little while, too, the big-headed baby under her flipper would send up a baby spout, as if in imitation of his mother.
"You must not think, however, that this lazy way of feeding was enough to keep the vast frame of the mother whale (she was quite sixty feet long: three times as long as Bill's shanty yonder) supplied with food.
This was just nibbling.

When she felt that her baby had nursed enough, she gave it a signal which it understood.

It fell a little back along her huge side.