All the Brothers Were Valiant by Ben Ames Williams.

All the Brothers Were Valiant by Ben Ames Williams.  
Joel Shore, newly appointed captain of the whaling ship Nathan Ross following his brother's apparent demise as captain of the same ship, elects to make his first cruise as captain to the very location where his brother had last been seen - the Gilbert Islands, in order to try to learn more about what happened to his brother. The focus of this tale is of that voyage halfway around the globe and the adventures which he and his crew encounter.