Still describing Walden Pond, Thoreau makes another of his mind-blowing statements. This one requires a bit of translation due to the archaic language:
“It is well to have some water in your neighborhood, to give buoyancy to and float the earth. One value even of the smallest well is, that when you look into it you see that earth is not continent but insular.”
Though I’d never thought about it that way, I immediately understood the observation that looking across water gives a sort of aesthetic buoyancy to the earth. But what does “not continent but insular” mean?
By “continent” he’s not referring to the seven continents of the globe, but using the word in the still-common sense of “incontinence.” What is “continent” holds its water.
Insular, in its original meaning, relates to an island.
He’s saying that the earth doesn’t hold the water, the water holds the earth. It isn’t that the land literally floats, but dry land is the exception on our planet. Water surrounds us in oceans, lies below us in aquifers, floats above us in clouds. So in a sense the dry land we experience as our day-to-day world is indeed insular and floating among the waters. Henry continues:
“This is as important as that it keeps butter cool. When I looked across the pond from this peak toward the Sudbury meadows, which in time of flood I distinguished elevated perhaps by a mirage in their seething valley, like a coin in a basin, all the earth beyond the pond appeared like a thin crust insulated and floated even by this small sheet of interverting water, and I was reminded that this on which I dwelt was but dry land.”
(About “A Year in Walden”)