AB, BC, AD, DC, may be plotted at the proper angles with each

it may be done with the chain only, if necessary.

Fully detailed Example of Chain Survey.-Fig. 24, Plate I., is an example of a larger survey measured with a 66 ft. chain. In this case it will be observed that a main chain line AB, 69.85 chains long, has been run through the centre of the survey. Upon it the triangles AFO, BEO, BCO, and ADO have been laid off, the remainder of the boundaries being taken up by the triangles OEF and OCD. The subsidiary chain line ao has been ranged in line with co in order to take in the road between a and o. Similarly the subsidiary chain line be takes up the longitudinal and cross fences shown. The chain line de is run for the same purpose, while the other lines fg and hk take up a footpath and a cross road respectively. It will be seen that upon plotting the four main triangles AFO, BEO, BCO, and ADO, the lines EF and CD which complete the other two triangles in this case act as tie lines to the previous four triangles. That is, the distances EF and CD should scale the same as measured on the ground. Each triangle should, however, have a separate tie line, so that any mistake may be traced to the triangle in which it occurs, otherwise in the event of an error the whole work might have to be rechained before the error was located.

In this case the subsidiary chain lines ao, bc, de, fg, and hk act as tie lines to all the triangles except the last, EOF. This triangle, however, should "check in " by the distance EF agreeing with that measured on the ground, when the other triangles have been plotted and checked.