During 1848- '49 he was chiefly occupied in astronomical, magnetic and latitude observations on the Florida Keys, as well as measurements of a preliminary base and triangulation near Key West and Bahia Monda, and from Key Biscayne towards Carysfoot reef. Again his work was carried on far into the winter season under adverse conditions, and in December and January, 1849-'50, we find him engaged in geodetic and magnetic observations at and off Cape Florida. After some summer field-work on the coast of New England, he returned in September to take charge of the computing department of the Coast Survey office, in which he continued through the years 1851-'52-'53. The efficient condition of that department during that time is specially referred to by the assistants in charge of the office, Captain Benham and Major Stevens, the latter saving: