Read it through once

It appears evident, then, that there is a distinct limit, as regards length, to all works of literary art—the limit of a single sitting—and that, although in certain classes of prose composition, such as “Robinson Crusoe” (demanding no unity), this limit may be advantageously overpassed, it can never properly be overpassed in a poem. Within this limit, the extent of a poem may be made to bear mathematical relation to its merit—in other words, to the excitement or elevation—again, in other words, to the degree of the true poetical effect which it is capable of inducing; for it is clear that the brevity must be in direct ratio to the intensity of the intended effect:—this, with one proviso—that a certain degree of duration is absolutely requisite for the production of any effect at all.