What two things does Nick see on or near the Queensboro Bridge that make him think that Gatsby is, perhaps, telling the truth?

From the text:

A dead man passed us in a hearse heaped with blooms, followed by two carriages with drawn blinds, and by more cheerful carriages for friends. The friends looked out at us with the tragic eyes and short upper lips of southeastern Europe, and I was glad that the sight of Gatsby’s splendid car was included in their sombre holiday. As we crossed Blackwell’s Island a limousine passed us, driven by a white chauffeur, in which sat three modish negroes, two bucks and a girl. I laughed aloud as the yolks of their eyeballs rolled toward us in haughty rivalry.

“Anything can happen now that we’ve slid over this bridge,” I thought; “anything at all. . . . ”

Even Gatsby could happen, without any particular wonder.