As indicated previously, Mosiah appears to be preparing for a potential political upheaval among his people. He would certainly hope for better, but appears to be preparing for the worst. In this case, he transfers items that had been part of his care into the hands of Alma. These items include the records and the interpreters. They do not include the Liahona nor the Sword of Laban. It appears that those items were much more tightly associated with the political rule.
It is fascinating that the records were turned over to Alma, as this returns the records to a patently religious line of transmission. The separate plate traditions begun by Nephi have been united under Benjamin (Amaleki gave the small plates to Benjamin; Omni 1:25) but now shift their transmission again, if only slightly.
Textual: In the 1830 edition the chapter ends with our verse 19. This verse is the beginning of a new chapter, and a new idea for Mormon the editor. Even this verse does not retain all of the impact of the original in that the 1830 edition has this as a single paragraph that continues to our current 29:1. In other words, this verse ends in the middle of a paragraph of the 1830 edition.
Paragraphs are much more modern markers than are chapter divisions. It is not clear at all that Mormon would have used paragraphs to tell his story, and likely did not. Unlike the chapter breaks that do appear to have some correlation to the plates, paragraphs may have been more at the whim of the translator and scribe. Thus there should not be too great of weight laid to the splitting of this paragraph.