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 proper 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 11 needs and de- 
