Fig. 5. Bevel Square
"Now, boys, I want to show you how we can make a fairly good chart simply by the use of this adjustable square, and this will also be of service to us in measuring heights of objects, as well as directing our course. It is now nine o'clock, and you will see that our pole (A) throws a shadow to the southwest. Supposing now, we direct the first leg of our journey to that large tree (C), to the west of us. If, now, we put one leg (D) of our rule along the shadow line, and the other leg (E) along the sight of the line (F), which goes to the tree, we shall find that the distance across between the ends of the bevel square is just two feet. It happens in this case that the tree (C) is due west from our observation point; so we have at nine o'clock each morning a means whereby we can always determine the true east and west."
"But supposing we lose our reckoning during the day, on account of cloudy weather, or by going through the forest, where we cannot make observations?"
Fig. 6. Sighting the Direction
"We could, probably, travel an entire day in one general direction, without being more than a few miles out of our course, north or south, and our direction immediately made out the next day."