Not that it was of any interest to him; merely to show his appreciation of the captain's confidence.

This could best be done by prolonging the conversation.
"Yes, up in the mountains of Brazil some'er's, I guess, though he don't say," answered the captain in a tone that showed that the subject was still open for discussion.
Mulligan now caught the friendly ball and tossed it back 'with: "I knowed a feller once who was in Brazil--so he said.

Purty hot down there, ain't it, captain ?" "Yes; on the coast.

I ain't never been back in the interior." Tod kept silent.

It was not his time to speak, nor would it be proper for him, nor necessary.