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A section has also been added on Geodesy. This branch of Surveying is extensively applied in the Coast Survey, and now forms an important element of a practi cal or scientific education.

A full account is also given of the manner of survey. ing the public lands; and, although the method is simple, it has, nevertheless, been productive of great results, by defining, with mathematical precision, the boundaries of lands in the new States, and thus settling their titles on an indisputable basis.

This method was originated by Col. Jared Mansfield, whose great acquirements in science introduced him to the notice of President Jefferson, by whom he was appointed surveyor-general of the North-Western Territory.

May it be permitted to one of his pupils, and a graduate of the Military Academy, further to add, that at the organization of the institution in 1812, he was appointed Professor of Natural and Experimental Philosophy. This situation he filled for sixteen years, when he withdrew from the Academy to spend the evening of his life in retirement and study. His pupils, who had listened to his instructions with delight, who honored his learning and wisdom, and had been brought near to him by his kind and simple manners, have placed his portrait in the public library, that the institution might possess an enduring memorial of one of its brightest ornaments and distinguished benefactors.

At the solicitation of several distinguished teachers, there is added, in the present edition, an article on Plane Sailing, most of which has been taken, by permission of the author, from an excellent work on Trigonometry and its applications, by Professor Charles W. Hackley.


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