It must have been a lovely place: everybody must have been so jolly.
From the way he talks, you'd think life here then was just one long midsummer serenade.

He declares it was always sunshine, that the air wasn't like the air anywhere else--that, as he remembers it, there always seemed to be gold-dust in the air.

I doubt it! I think it doesn't seem to be duller air to him now just on account of having a little soot in it sometimes, but probably because he was twenty years younger then.
It seems to me the gold-dust he thinks was here is just his being young that he remembers.

I think it was just youth.

It is pretty pleasant to be young, isn't it ?" She laughed absently, then appeared to become wistful.