4 A MANUAL OF TOPOGKAPHIC METHODS. 



through the states of New York, New Jersey, Pennsylvania, Maryland, 

 Virginia, West Virginia, North Carolina, Tennessee, Georgia, and Alabama. 

 The work of connecting the Atlantic and Pacific coasts has been carried 

 far toward completion, a belt having been extended westward from the 

 head of Chesapeake Bay into central Kansas. A base lias been measured 

 near Colorado Springs, Colorado, and work has been extended thence east- 

 ward to the east boundary of the state, while from the Pacific coast triangu- 

 lation has been brought eastward across California, Nevada and Utah. 



In assisting the state surveys, the Coast and Geodetic Survey lias, 

 moreover, done a considerable amount of triangulation in the states of Mas- 

 sachusetts, New York, New Jersey, Pennsylvania, Kentucky, Tennessee, 

 and Wisconsin. 



The United States Lake Survey has mapped the shores of the Great 

 lakes, carrying triangulation around them, and connecting the head of Lake 

 Michigan with the foot of Lake Erie. A belt of triangulation has also been 

 earned from the neighborhood of Vincennes, Indiana, northward along the 

 eastern border of Illinois, connecting with the triangulation on the shore of 

 Lake Michigan. 



The Engineer Corps, U. S. Army, has completed a number of small 

 pieces of topographic work in different parts of the country, and is now 

 engaged in mapping the course of the Mississippi and Missouri rivers, con- 

 trolling the work by geodetic methods. 



The surveys of the General Land Office have extended over an area 

 of about a million and a half square miles, and plats have been prepared 

 representing the drainage of this entire area. The quality of this work is 

 of varying degrees of excellence, but from its inception in the early part 

 of the century its quality has improved greatly. Most of this work can be 

 utilized either directly or indirectly by methods to be detailed hereafter. 



SURVEYS UNDER STATE GOVERNMENTS. 



Massachusetts. — Between 1830 and 1842, the state of Massachusetts 

 carried on what was for the time an elaborate system of triangulation, 

 known as the Borden Survey. By this organization numerous points, in 

 the aggregate several hundred, were determined within the limits of the 



