SURVEYING INSTRUMENTS, 



SURVEYOR'S LAND CHAIN. 



GUNTER'S Chain (Fig. 77, page 51) is the one now com- 

 monly used in taking the dimensions of land ; it is sixty-six 

 feet, or four poles, in length, and is divided into 100 links, 

 each of which is joined to the next by three rings; the 

 length of each link, including the connecting rings, is 7.92 

 inches, and at the end of every tenth link is attached a piece 

 of brass (each of a different shape) for more readily count- 

 ing the odd links. 



Short distances, or offsets from the chain line, are usually 

 measured with a rod, called an off-set staff, the most con- 

 venient length for which is 6 feet 7.2 inches, being equal to 

 10 links of the chain, and it should be divided accordingly. 



With the chain should be provided ten arrows, which may 

 be made of strong iron wire, about 12 or 15 inches long, 

 pointed at one end for piercing the ground, and turned up 

 at the other, in the form of a ring, to serve as a handle: 

 their use is to fix in the ground at each extremity of the 

 chain whilst measuring, and to point out the number of 

 chains measured. Price, 2 pole, $1.00 and $1.25. 



" 4 " $2.25 to $2.75. 



Perambulator, or Measuring Wheel. (Fig. 78, page 51.) 

 An instrument which being run along a road or other 

 level surface indicates and registers the exact distance it 

 passes over. The general form of the instrument, and its 

 system of wheel-work, are as follows : 



The wheel is 8^- feet in circumference, and consequently 



measures exactly a pole in every two revolutions. The 



number of revolutions made, and consequently the distance 



passed over, is seen on the dial-plate, where there are two 



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