Carry On, Mr. Bowditch / he novel introduces readers to young Nathaniel "Nat" Bowditch, the son of a ship captain. Nat loves school, especially mathematics. He dreams of someday attending Cambridge's Harvard University, but is forced by economic circumstances to quit school and help his father at the coopering. Eventually, he ends up as an indentured servant to a ship's chandler. Still determined to continue his education, and compelled to work for the chandlery for nine long years, he begins to teach himself Latin. After being granted access to a local private library, he continues to study and to master mathematics in the evenings after work.
When his indenture is complete, he gets the chance to go to sea. There, he discovers that many of the navigational sources used at the time contain extensive and dangerous errors. He is prompted to compile a new book of navigational information. This book, The American Practical Navigator, is still in use today. Under Captain Prince, Nat learns how things work at sea. He invents a new way of working a lunar, increasing the accuracy of calculations used to find ships' locations. He also teaches the crew on the ships about navigation. It took a while for the men to understand, but when they did understand, the men, such as Lem Harvey, the crew's troublemaker, felt smart and important. He also let Little Johnny look through a sextant and search for Polaris. Eventually Nat becomes a captain himself. In the course of the book, Nat receives a Master of Arts degree from the school he always wanted to attend, Harvard.
