Deposition is testimony given under oath. It is part of the fact-collection process that takes place outside of trial, generally before the trial begins. It is a more private format, and does not take place in a courtroom. Usually it consists of a series of questions and answers, the questions posed by an attorney and the answers provided by the sworn-in witness.
The first passage presents factual information about the Mississippi River, while the second passage simply uses the Mississippi River for plot points and setting.
