Verse 38 is the first time we learn that the “ball, or director” had been called the Liahona. Why does this information come so late in the text? Part of the answer is that it may or may not have been mentioned in the part of the translation of Mormon’s text that was lost (the 116 pages). Perhaps it was known then. Nevertheless, it was apparently known better as the “ball or director,” since that is the term Alma expects Helaman to know. The name Liahona was apparently a word with a lost meaning, as Alma declares that it means, “being interpreted, a compass.” Rather than an object name, it may have simply been a description in a language, or at least a word in that language, which had lost its meaning by Alma’s day, where the word “ball, or director” had not.
Verses 39 through 42 recount the way that the Liahona worked. Alma tells this part of the story to Helaman because by his day the Liahona was simply a sacred artifact. It appears to have ceased to function in the New World. Thus, Helaman may not have understood what its original function was. Alma needs to make certain that Helaman knows how it worked so that it can become the object lesson he wants to teach.