When the three friends stopped for lunch below the Monkey Islands, what did the narrator have a sudden urge for? What was the alternative they...

This incident happens in Chapter XII of Three Men in a Boat. The men stop for lunch and eat cold beef. No one had remembered to pack mustard, however; and at least Harris and the narrator long to have some mustard to garnish the beef. This is one of many examples when just the lightest tidbit or slightest situation can set the characters into a funk or a tizzy. Or at least it seems this way, when described by the narrator:

It cast a gloom over the boat, there being no mustard. We ate our beef in silence. Existence seemed hollow and uninteresting. We thought of the happy days of childhood, and sighed. We brightened up a bit, however, over the apple-tart, and, when George drew out a tin of pine-apple from the bottom of the hamper, and rolled it into the middle of the boat, we felt that life was worth living after all.

But the friends had not packed a can opener either. Thus follows another one of the humorous scenes in the book. The men try using every heavy or sharp implement they find to open the can: a pocket knife, a stone, the boat mast, whatever is in sight. Nothing works. The can eventually ends up in the river, unopened.