Answer:
Daily record of events and as evidence for the Catholic Monarchs.
Explanation:
Several contemporary references confirm Columbus kept a journal of his voyage as a daily record of events and as evidence for the Catholic Monarchs. Upon his return to Spain in the spring of 1493, Columbus presented the journal to Isabella I of Castile.
He kept a journal so when he returned to Spain, he can show the King and Queen what did he find.
