This is because the waking consciousness is beginning to shut out the world-- and its set of ideas.
So consistent is the system that even if Waking Reason abstract itself, not to sleep, but to think on one subject such as writing a poem or inventing a machine, certain affinities will sleep or dreams begin to show themselves.

When Genius is really at work, it sweeps along, as it were, in a current, albeit it has enough reason left to also use the rudder and oars, or spread and manage a sail.

The reason for the greater fullness of unusual images and associations (_i.

e._, the action of genius) during the time when one is bent on intellectual invention is that the more the waking conscious Reason drowses or approaches to sleep, the more do many images in Memory awaken and begin to shyly open the doors of their cells and peep out.
In the dream we also proceed, or rather drift, loosely on a current, but are without oars, rudder or sail.

We are hurtled against, or hurried away from the islands of Images or Ideas, that is to say, all kinds of memories, and our course is managed or impelled, or guided by tricky water-sprites, whose minds are all on mischief bent or only idle merriment.