Conversation so far:
What was Matthew Fontaine Maury's early career like?
Matthew Fontaine Maury joined the Navy as a midshipman on board the frigate Brandywine which was carrying the Marquis de La Fayette home to France.
What did Matthew Fontaine Maury achieve?
In 1855 Matthew Fontaine Maury published the first modern oceanographic text, The Physical Geography of the Sea.
What was Matthew Fontaine Maury's early life like?
Matthew Fontaine Maury's father forbade him from joining the Navy due to Maury's older brother's death. Maury obtained a naval appointment through a family friend at the age of 19.
What did Matthew Fontaine Maury do after obtaining naval appointment?
Almost immediately, Matthew Fontaine Maury began to study the seas and to record methods of navigation.

Question: What methods of navigation did he use?
Self-contained rewrite: What methods of navigation did Matthew Fontaine Maury use?