A new transit instrument, imported by the United States government for the use of the Northeastern Boundary Commission, was set up in December, and used during the winter in observations for ascertaining the latitude, as previously described in the quotation from Prof. Peirce. The results were collated and discussed by Prof. Peirce in the memoirs of the American Academy. These were the first notable observations of precision at the new observatory. The longitude was also determined by the most accurate method then known, observation of occultations and moon culminations and comparison of a considerable number of chronometers transported to and from Greenwich by ocean steamers. In the ultimate determination the record made by several hundred chronometers thus sent to and fro, and observations of occultations, etc., in Dorchester, Cambridge, Brooklyn, Philadelphia and Washington, ranging through many years, were brought into the account. The earliest were observations made in Philadelphia in 1769. After the laying of the Atlantic cable still closer comparisons with the zero of Greenwich were possible. The position of the observatory as finally determined and now officially of record is: Longitude, 71° 7′ 44.85″, west; latitude, 42° 22′ 47.6″, north. As showing the error of the best attainable results by use of chronometers it may be remarked that by that method the central tower of the observatory was located at a point on the lawn half way between the front door of the director’s dwelling house and Garden street. The discrepancy is about 320 feet. About the time of the first determination Commodore Owen of the British Navy was making an official survey of the coast of New Brunswick and Nova Scotia. Having confidence in what had been done at Cambridge he took that station for his zero in preparing his official report, ultimate reference being made to Greenwich. The first importation of chronometers appears to have been made jointly by Prof. Bond and Commodore Owen. When the report was submitted it was challenged by some of the British Board of Admiralty, who believed that the longitude of Halifax was better known. In due course Prof. Bond was inquired of, and his letter addressed to the board of admiralty, in explanation of the technicalities, proved convincing and its conclusions were cordially accepted, with thanks by Admiral Beaufort on behalf of the board. The officers-in-chief of the United States Coast Survey, and of the exploring expedition severally adopted the Cambridge meridian as the zero in preparing their official reports. A new instrument purchased by the observatory, a 2¾-inch equatorial, permitted accurate observations to be made of the solar eclipses of 1845 and 1846, the comets of the same years, the transit of Mercury in 1845 and of the newly discovered planet Neptune.