14 A MANUAL FOR NORTHERN WOODSMEN 



sary to chain by the top, not the bottom, of the pins. No 

 jerking of the chain should be allowed. The rear man 

 should not stop the head man with a jerk. The head man 

 must pull steadily on the chain when measuring. 



When chaining on slopes which are so steep that the 

 full length of the chain cannot be levelled at once, the 

 head man first draws the chain forward the whole length 

 and in line. He then drops the chain and his marking 

 pins and returns to a point where he can level a part of the 

 chain. This distance is measured and one of the rear man's 

 pins stuck at the point. The rear man then comes forward 

 and, taking the chain at the same point, holds it to the 

 mark while a second section is measured, and so on till the 

 end of the chain is reached, when the head man sticks one 

 of his own pins. It is not usually necessary to note the 

 lengths of the parts of the chain measured. Take care 

 only to measure to and from the same points in the chain 

 and not to lose the count by getting the marking-pins of 

 the two men mixed together. 



Accuracy. The requirements of woods chainage vary 

 so widely, its difficulties are sometimes so great, and the 

 expense permissible for the work is often so restricted that 

 only guarded statements can be made as to obtainable 

 accuracy. When chainmen, measuring the same line 

 twice, agree almost exactly, it does not prove that they 

 have given correct chainage, for two other men on the 

 same line may get a result considerably variant. Really 

 correct chainage is to be obtained only by strict attention 

 to the sources of error mentioned above, their amount and 

 nature. In general, it may be said that on smooth and 

 level ground, free from obstructions, chaining may be 

 done with error of a very few feet in the mile. On land as 

 it runs, however, chainage accurate to within a rod in a 

 mile is generally called entirely satisfactory. 



Summary. Good chaining consists in keeping the chain 

 of right length, in true alignment, vertical and horizontal, 

 and in projxjr stretching, marking, and scoring. It is a 

 very important part of all surveying which employs that 

 method of measuring distance, and has been badly neg- 

 lected in much woods work of the past. It needs ami <le- 



