In "Once More to the Lake," why does White feel disconcerted that the road to the farmhouse has two tracks, not three?

"Once More to the Lake" is White's bittersweet story of returning to the fishing camp on the lake in Maine where he had spent a month each summer with his family when he was a boy. When White goes back to the lake, he takes his own son with him. Before arriving, he wonders what the lake will be like, now that so many years have passed:

I wondered how time would have marred this unique, this holy spot--the coves and streams, the hills that the sun set behind, the camps and the paths behind the camps.

Once there and settled with his son, White feels that being at the lake will be the same has it once had been. Being in the familiar place, doing the familiar things creates another feeling, as well. As he watches his son do what he himself used to do as a child, he envisions his son as the boy he used to be, and sees himself as his own father:

I began to sustain the illusion that he was I, and therefore, by simple transposition, that I was my father. This sensation persisted, kept cropping up all the time we were there.

This passage relates to the theme of time and its passing that is introduced in the beginning, and it will occur throughout the remainder of the essay. White's illusion is that time hasn't passed at all. White's illusion persists as he watches his son fish, just as he had once fished:

There had been no years between the ducking of this dragonfly and the other one--the one that was part of memory.

It is enhanced by the sight of other campers swimming in the lake, one batheing with a bar of soap:

Over the years there had been this person with the cake of soap, this cultist, and here he was. There had been no years.

"There had been no years" has become the primary motif in the story, until White and his son walk to the farmhouse for dinner and discover the two wagon tracks:

Up to the farmhouse to dinner through the teeming, dusty field, the road under our sneakers was only a two-track road. The middle track was missing, the one with the marks of the hooves and the splotches of dried, flaky manure. There had always been three tracks to choose from in choosing which track to walk in; now the choice was narrowed down to two. For a moment I missed terribly the middle alternative.

White is disconcerted to find only two tracks in the dusty road where three had once been because it jars his illusionary sense of the past's being preserved in this special place, his momentary peace in feeling "[t]here had been no years." The absence of the third track, a memory from his childhood, reminds him of the reality that years have passed and will continue to pass. His son will grow up, just as he grew up.