Read it through once

The next point to be considered was the mode of bringing together the lover and the Raven—and the first branch of this consideration was the locale. For this the most natural suggestion might seem to be a forest, or the fields—but it has always appeared to me that a close circumscription of space is absolutely necessary to the effect of insulated incident: it has the force of a frame to a picture. It has an indisputable moral power in keeping concentrated the attention, and, of course, must not be confounded with mere unity of place.