The archaeological journal from 1928 speaks of "methane smell" but methane and indeed natural gas are usually odorless. The typical gas smell associated with natural gas today is the result of another chemical intentionally added to it precisely so people can smell it, and thus notice gas leaks more easily. This practice was widely adopted only in 1937 after a deadly school explosion in New London, Texas.
Even though Marcus was getting late, he stayed back to discuss the case.