After this work was completed and the results published in 1885, nothing was done in this line by the Bureau of Navigation for some years. Upon the return of the writer in the spring of 1888, from a cruise in the South Pacific, he found that the subject of sending an expedition to complete the measurements in Mexico and Central America was under consideration in the Bureau of Navigation and the Hydrographic office. It was finally decided that the work should be done, and the writer was placed in charge. The instruments were brought out of their retirement, and by the aid of the Hydrographic Office a very complete outfit was furnished, and in November of last year a start was made from New York, the expedition proceeding by mail steamer to Vera Cruz. Here the spot occupied by Lieut. Com. Davis in '83 was found, his transit pier, which was still standing was repaired, and instruments mounted. Lieut. Charles Laird, U. S. N., who had been identified with the longitude work since the China expedition in 1881, was left in charge of the observatory at Vera Cruz, and the writer proceeded with his party to the small town of Coatzacoalcos, at the mouth of the river of the same name. This point is about one hundred and twenty miles southeast of Vera Cruz, and is the landing place of the cable. A land line extends from this point to Salina Cruz on the Pacific coast, a distance of about two hundred miles. In exchanging time signals between Vera Cruz and Coatzacoalcos, the automatic method was employed, the cable being short. The old wooden observatories were used at these points, but as they were too heavy for transportation across the Isthmus, tents made especially for astronomical purposes were substituted for them in the observations made on the Pacific coast. The journey across the Isthmus was slow, about two weeks being employed in traveling two hundred miles, though as the route was devious, the actual distance was nearer three hundred. Some of the instruments were heavy, and after being taken in canoes a hundred miles up the Coatzacoalcos river, against a rapid current, they were loaded on a train of pack mules, and carried the rest of the way by land. While the first party was crossing the Isthmus, the other was on its way from Vera Cruz, and being ready at about the same time, a successful measurement was made between Coatzacoalcos and Salina Cruz, exchanging signals automatically. The Coatzacoalcos party then crossed to Salina Cruz, while the other proceeded to La Libertad in Salvador, where the station established in the Spring of '84, was again occupied. The measurement between these places being completed, the Libertad party went on to San Juan del Sur, in Nicaragua, near the terminus of the proposed interoceanic canal. In the measurement between this point and Salina Cruz, as well as in the one preceding, the exchange was effected by mirror signals. This completed the season's work, and the two parties made the best of their way home via Panama, arriving in Washington in April and May respectively. The computation of the observations is not yet complete though well advanced; it was the intention to publish preliminary results this Fall, but owing to lack of time that can not be done.