Surveying chains are made of steel or iron wire. At every 10 links from each end of the chain a piece of brass known as a teller or marker is attached, as shown in the figures. These markers are notched to indicate the number of links in tens from each end up to the fiftieth link or middle of the chain. Thus a reference to the figure shows that the first marker indicates 10 links from one end or 90 links from the other; a marker with two points indicates 20 links from one end and 80 links from the other; three points, 30 links from one end, and 70 links from the other; four points, 40 links from one and 60 links from the other; while the fiftieth or middle link has a circular marker attached. By means of these markers any distance is easily reckoned.

In using a chain, two operators are required - one to lead and one to follow. The follower holds the chain by means of the ring at end fairly against the post from which a start is to be made. The leader (tig. 400) takes the other end of the chain and walks in a straight line towards a definite point, indicated by a staff. He carries ten arrows, one of which he places at the end of each chain that is measured (see fig. 399). The follower then moves forward and holds his end of the chain against the arrow left by the leader. The latter proceeds to the length of the chain and fixes the second arrow in the ground. The follower then takes up arrow No. 1, and holds the end of the chain at the point where the leader has fixed arrow No. 2, and so on to the finish. If less than ten chains are measured, the number of arrows left in the leader's hands will show how much has been unchained, the arrows in the follower's hand, of course, representing the distance covered. Any distance less than a chain is measured in links, and the brass markers on the chain indicate the number of links as above stated.

Chain Leader.

Fig. 400. - Chain Leader.