To do that I must find the line between the sycamore and the pine.

Now you go over there beyond the pine, and take sight on it at the sycamore till you get the two trees in a line with you.

Then I'll stand over here, between the two object trees, and move to the right or left as you tell me to do, till you find that I am exactly in the line between them.

Then I can pick out the right tree ahead." Sid did as he was told, the boys all looking on with great interest, and presently Sam had selected their next object tree.

The boys were astonished greatly at what they thought Sam's marvellous knowledge, but to their wondering comments Sam replied:-- "I haven't done anything wonderful.