20 



AGRICULTURAL ENGINEERING 



Equivalent Table 





Sq. ch. Sq. rd. 



Sq. li. 



10 160 



100,000 



1 16 



10,000 



1 



625 



Surveyor's Measure. 



625 square links (sq. li.) make 1 square rod (sq. rd.) 

 16 " rods " 1 " chain (sq. ch.) 



10 " chains " 1 acre 



640 acres " 1 square mile, or one section 



A. 



Cloth and Metallic Tapes. Tapes made of linen cloth 

 are not practical to use in land surveying, even when well 

 made and water-proofed. They will stretch when pulled up 

 tight, and are difficult to handle in the wind. A cloth 

 tape is much improved when small brass wires are woven 

 lengthwise into it to check the tendency to stretch. Such 

 a tape is said to be a metallic tape. These tapes are made to 

 wind into a case of sheet metal or leather, and for this reason 



are very convenient to carry about. 

 Steel Tapes. The steel tape is 

 now the standard measuring in- 

 strument, as it has many advan- 

 tages. It does not kink, stretch, or 

 wear so as to change its length. 

 The steel tape may be obtained in 

 lengths varying from 3 feet to 1000 

 feet. These tapes may be marked 

 or graduated in any form desired. 

 The two common methods of 

 marking the tape are by either 

 etching the surface with acid, or stamping the marks on 

 solder placed on the tape at the desired places. A tape 



Fig. 2. A metallic tape. 

 This tape has brass or cop- 

 per wires woven into it 

 lengthwise. 



