At the beginning of this chapter, Mormon and his father go south to fight against the Lamanites, and are victorious. After describing how wicked the Nephites have become, Mormon notes that there were also many Gadianton robbers who “did infest the land, insomuch that the inhabitants thereof began to hide up their treasures in the earth.”
In 4 Nephi 1:46, Mormon had noted that the Gadiantons had made a reappearance, and “gold and silver did they lay up in store in abundance, and did traffic in all manner of traffic.” That desire for the gold and silver apparently led to some attempting to hide their own wealth so that the Gadiantons could not have access to it.
In a Mesoamerican context, these Gadiantons would probably be the people of Teotihuacan. During this time period they were a very powerful city and people, and they were actively expanding their trade routes into the areas where we believe the Nephites would have been, as well as further south into Lamanite territory. This would be the reason that 4 Nephi 1:46 spoke of them as “[trafficking] in all manner of traffic.”
The “sorceries, and witchcrafts, and magics” of verse 19 plausibly refer to the foreign religion that was infesting the land along with the Gadiantons who would have brought that religion.
This is not the end of a chapter in the 1830 edition of the Book of Mormon.