In chapter 13 of Life on the Mississippi, Mark Twain introduces a pilot named Brown and describes him by his memory. "Somebody would mention a name. Instantly Mr. Brown would break in—'Oh, I knew him. Sallow-faced, red-headed fellow, with a little scar on the side of his throat, like a splinter under the flesh.'" Brown can't let any fact go. He sets out to tell you a funny story about a dog and ends up covering the dog's breed, its owner, the owner's family, and the family's weddings and burials, and he never gets to the dog. In Brown's case a name is what sets the whole machine going.
Five chapters later Twain brings him back as "the man referred to in a former chapter, whose memory was so good and tiresome," and the cub Sam Clemens reports to his pilot-house on the Pennsylvania. Brown stands at the wheel and ignores him for ten minutes. Then he looks the boy over "from head to heel for about—as it seemed to me—a quarter of an hour," and asks his first question:
'Are you Horace Bigsby's cub?'
The boy's teacher is Horace Bixby, and the book names him sixty-nine times, always spelled Bixby. "Bigsby" appears exactly once, and Brown is the one who says it.
A few lines down, Twain adds this:
'What's your name?'
I told him. He repeated it after me. It was probably the only thing he ever forgot; for although I was with him many months he never addressed himself to me in any other way than 'Here!'
I noticed the word one evening while reading, and it took me two evenings to decide what I thought of it. I'm writing up the process because I enjoyed it, and because the cheap step and the useful step turned out to be different steps.
Typo or joke
There are two ways to read the line, and both have support.
The first is that it's a slip. The book stitches together older material and new writing, and a misspelling that survives in one spot is about as common an error as books have. I happen to like this kind of error. I had just finished a piece about a government webpage that had been edited everywhere except one paragraph, and that one paragraph gave the whole edit away.
The second is that it's deliberate. Brown recognizes every name he hears and also gets this one wrong. Within the same exchange the narrator says names are the one thing Brown forgets. If you put a misheard name directly ahead of the line "the only thing he ever forgot," that sounds like a writer arranging a setup.
The case against the joke is that Twain rarely lets a joke pass without pointing at it. Here he doesn't wink, doesn't add "Bigsby, he called him," and doesn't come back to it. The word just sits on the page.
The cheap test
My copy was the Project Gutenberg text, and a transcription can't tell you what the 1883 printing said. A volunteer typist could have produced "Bigsby" as easily as Twain could have. So I went to the Internet Archive, downloaded the OCR text of six 1883 scans (three copies of the Osgood first edition, plus the Harper, Chatto & Windus, and Dawson printings), and counted. OCR noise put the Bixby totals anywhere from 41 to 71. Bigsby came up once in every edition.
That ruled out a Gutenberg error. The spelling was in the book from the first printing. It still didn't tell me whether anyone meant it, because a count can't show intent.
The useful test
So I opened the page image itself: Osgood first edition, page 218, under the running head "MY NEW TUTOR," last line: Are you Horace Bigsby's cub?
Then I turned to the facing page, which I nearly skipped.
Page 219 is a full-page illustration, and its caption is the same line: "ARE YOU HORACE BIGSBY'S CUB?" The List of Illustrations at the front of the book lists it again as number 115. So the misspelling was typeset three times, in the text, in the caption, and in the index. Someone working on the book went through this chapter and picked that line as the one to illustrate. Unless they were skimming, they read "Bigsby," and they left it alone.
Looking at the earlier text helped too. The Mississippi chapters started out as "Old Times on the Mississippi," a series Twain ran in the Atlantic in 1875. I checked an 1876 reprint, and it never names Bixby at all. He appears only as "Mr. B——." The name was added for the 1883 book, so every "Bixby" in Life on the Mississippi was filled in at that point. Chapter 18 isn't in the 1875 series, though. Brown's section is new writing from 1883, so "Bigsby" can't be a scrap left over from the magazine version. It went into the text along with everything around it.
Where I come out
I can't prove it either way. The manuscript would settle the question, and I haven't seen it. My own estimate moved from roughly even to about seventy-thirty in favor of a deliberate joke. That estimate rests on three things: Brown's memory runs on names, the forgetting line comes a few lines after the mistake, and the misspelling survived the person who chose the caption.
The method is the part I'll actually keep. The count was quick, and all it showed was that the question was real. Two page images answered it, and the more important of the two was the page I hadn't planned to look at.
There's also a reason the joke works if it is one. Chapter 18 is full of things Brown can't get right and won't own up to. He criticizes the cub for hugging a bar and for not hugging it, for firing up without orders and for waiting for them. In his pilot-house the boy is wrong before he does anything. A man who already knows everything about everyone has no need to learn a cub's name, or to get his boss's name right. He calls the boy "Here!", and to Brown the teacher becomes Bigsby. Twain doesn't point at it. The book just records what Brown said.