102 A MANUAL OF TOPOGEAPHIC METHODS. 



The supervision of the surveys is vested in surveyors-general, one in 

 each state or territory in which such surveys are being carried on. The 

 surveys are made by contract, at certain stated prices per linear mile, and 

 are subject to examination by salaried officers of the Land Office. 



The initial work consists in the measurement of a principal meridian 

 and a base line, their intersection being the initial point of the survey. 

 These lines are run with considerable care. The principal meridian may 

 be run both northward and southward from the initial point, and the 

 instructions require that observations be made for azimuth at intervals not 

 greater than 12 miles, and that the line be double chained, two sets of chain- 

 men being employed for that purpose. In measuring a base line, which is 

 to follow as closely as possible a parallel of latitude, in case the theodolite 

 be used'it is to be run by means of a succession of tangents to the parallel, 

 not exceeding 12 miles in length. At intervals of half a mile a point on the 

 parallel is marked by offsets from the tangent line, and at the end of 12 

 miles a new tangent is commenced. In case it be run by solar compass, it 

 must be checked by latitude observations at intervals of 12 miles. The base 

 line may be run either east or west from the principal meridian. At inter- 

 vals of 24 miles on the base line auxiliary meridians are run in the same 

 manner as prescribed for the principal meridian, and, at intervals of 

 24 miles on the meridian, correction lines are run east and west in a 

 similar manner. It is only recently that the interval between guide merid- 

 ians and correction lines has been reduced to 24 miles, or 4 townships. 

 Heretofore the intervals have differed at different times, but have in all cases 

 been greater. These lines are run with a solar compass or theodolite, and 

 never in later years with the ordinary compass, and all these lines double 

 chained. 



By this means the country is divided into approximate squares 24 miles 

 on a side. Each such area is then divided into townships approximately 6 

 miles on a side. The east and west sides of these townships are meridians 

 which are run northward from the base line or from the correction line, 

 having a breadth upon the base or correction line of G miles, but decreasing 

 in breadth with the convergence of the meridians. The north and south 

 sides of the townships may be run east or west, as the case may be. The 



