The previous idea of Ireland being eternal is supported by the view according to which its history stretches to immemorial times: "Every layer they strip/Seems camped on before./The bogholes might be Atlantic seepage./The wet centre is bottomless" (Heaney, 25-28). The fact that the centre is wet suggests the constant and eternal vitality of existence's root. The values of the people living in Bogland can not get weary because they have such a solid source.

If Bogland is the place where the poet comes from, in Yeats' case, Innisfree is the place where he wishes to escape. The environment is simple and just like in the poem analyzed above, the island is a symbol of freedom. In addition, the isolation allows the poet to come in touch with himself.

The island can be a considered a metaphor of the self, since through its characteristics it favors both the construction and the discovery of the self. Unlike Heaney who lives in a country where there are no fences and where people are free and do not limit each other, Yeats wishes to escape from his contemporaries in order to find his peace. From this point-of-view, Innisfree becomes the symbol of paradise.

The poet's fantasy creates it. It could be safe to assume that just like in the case of Heaney we are dealing with mentalscapes, not only landscapes "And I shall have some peace there, for peace comes dropping slow,/Dropping from the veils of the morning to where the cricket sings;/There midnight's all glimmer, and noon a purple glow, / And evening full of the linnet's wings" (Yeats, 5-8). If Bogland was an eternal land, Innisfreeis situated out of time. The fact that "peace comes dropping slow" is a clear suggestion of time's...

The poet explains that this is not a purpose he might have set for himself from various reasons, but it is a calling from the inside: "night and day / I hear lake water lapping with low sounds by the shore;/While I stand on the roadway, or on the pavements grey, / I hear it the deep heart's core" (Yeats, 9-12). The water and the island are symbols of freedom. From the associations that the poet makes, the readers understand that the island is the only place where he can be himself. The waters of the lake are also a symbol of stability and of protection. There is a clear opposition between the civilized world, symbolized by the grey pavement and the natural world dominated by color. The descriptions provide us with insight about the manner in which the poet perceives the surrounding environment.
In conclusion, both the poems are describing ideal islands, places where eternity and infinity are found together. If in Heaney's case, the island is his home, for Yeats it is the ideal home. The most important feature of the islands however is that they allow for internal freedom and the discovery of the self (and in fact the island through its solitude is itself the very symbol of the individual self).

Bibliography:

Meredith, D. "Landscape or mindscape? Seamus Heaney's Bogs," Retrieved October 11, 2010 from http://78.137.164.74/~geograph/irishgeography/v32-2/bogs.pdf

Heaney, Seamus. "Bogland"

Yeats, W.B. "The Lake Island of Innisfree"