In John Dewey's How We Think, there is an example of someone reflecting on the purpose of a particular part of a boat:
Projecting nearly horizontally from the upper deck of the ferryboat on which I daily cross the river, is a long white pole, bearing a gilded ball at its tip. It suggested a flagpole when I first saw it; its color shape, and gilded ball agreed with this idea, and these reasons seemed to justify me in this belief. But soon difficulties presented themselves. The pole was nearly horizontal, an unusual position for a flagpole; in the next place, there was no pulley, ring, or cord by which to attach a flag; finally, there were elsewhere two vertical staffs from which flags were occasionally flown.
After a bit of reasoning (which you can see in #2 here), the person decides what he thinks the 'pole' is for.
I formed the conclusion that the pole was set up for the purpose of showing the pilot the direction in which the boat pointed, to enable him to steer correctly.
However, Dewey never provides the name of the actual part. I've been looking around for a word to describe this so that I can find a picture of it! I found this list of words and thought it might be a 'bowsprit' or a 'jibboom'. Both are excellent words but may be inaccurate.
Looking up 'ferryboat' does not help; I think ferries have changed so much since 1910 that finding a matching word, description, or picture using this search term alone is not going to be possible!
In both these pictures, you might just about see the part I'm talking about as a dark line angling up and out from the upper deck, in front of the bridge. Assuming that I've read Dewey's description correctly, that is.
I think I have found a clearer picture of what I'm looking for (or is this just a standard flagstaff?) -- see the Eureka, an 1890 ferryboat. But is the end shown below the stern or the bow? [Source.]