At one end of the gondola, largely oblivious to the coming and going on deck, with his tail thumping expressively now and then against the planking, and his nose among the pages of a volume by Mr. Henry James, lay a dog of no particular breed, to all appearances absorbed in the text before him.
* * * * * * * * * *
It's possible all of Thomas Pynchon's novels are trying to bring to light the CIA's experiments with making hyper-intelligent canines. Or maybe as a youth, Pynchon had a dog with whom he had long conversations. I don't think this dog talks like the dog in Mason & Dixon or the dog in Gravity's Rainbow that was trying to avoid capture when Pointsman got his foot stuck in the toilet. What the hell was that about anyway?
"'Why it's Mrs. Nussbaum!' Roger cries, the same way he's heard Fred Allen do, Wednesday nights over the BBC.
'You vere ekshpecting maybe Lessie?' replies the dog."
I get it! Gravity's Rainbow is a truly weird novel. But am I supposed to take the dog's reply literally?! Oh wait! I remember now! Occasionally the narration slips into other kinds of media based on a brief fantasy pinging through the mind of the character through whose perspective the book is currently focused. So here he just imagines the dog finishing up the Fred Allen bit in the voice of Mrs. Nussbaum. I imagine little Thomas Pynchon probably huddled up to the radio each week to listen to The Fred Allen Show, crying snot from laughing so hard.
My supposition is that the dog is "of no particular breed" because that's a way to describe all the lads aboard the Inconvenience. In a way, being an adventuring aeronaut in a small tightknit club, you transcend class and race (literally as well as figuratively being that they're in an airship. Is that the reason for their being in an airship?!). Your crewmates are your siblings, your family, your classless class outside the rigid bounds of society. They're all just mutts absorbed in a book.
While the dog is actually absorbed in a book (a Henry James novel that will later be identified by plot), the Chums of Chance are "absorbed in the text" in a completely different way. They are literally characters in a series of books while also literally being characters in Against the Day. Sorry for using literally twice in one sentence and for practically no reason at all. I probably should have coined the term "literaturally" instead.
This dog is possibly also an acknowledgment of the readership. As we read Thomas Pynchon in public (the best place to read it so that other people know you're a smartie!), we also ignore the coming and going all around us. And we're probably expressing our pleasure in an outward manner like the dog thumping its tail except we're laughing a little too loudly and trying to make eye contact in a melodramatic effort to show how much we understand this big fat Thomas Pynchon book we're reading.