Manual for Noncommissioned Officers and Privates of Cavalry of the Army / of the United States 1917. To be also used by Engineer Companies (Mounted) for Cavalry Instruction and Training

by United States. War Department

Water flows down hill. If you are in the bed of a stream, contours representing higher ground must be to your right and to your left. Get the elevations of these contours. Generally the nearest contour to the bank of the stream will cross the stream, and there will be an angle or sharp turn in the contour at this crossing. If the point of the angle or sharp turn is toward you, you are going downstream; if away from you, you are going upstream.

If the contours are numbered, you have only to look at the numbers to say where the low and where the high places are; but to read a map with any speed one must be quite independent of these numbers. In ordinary map reading look, first of all, for the stream lines. The streams are the skeleton upon which the whole map is hung. Then pick out the hilltops and ridges, and you have a body to clothe with all the details that will be revealed by a close and careful study of what the map maker has recorded.

As to closed contours, they may outline a depression or a hill On the map "881" or "885" might be hills or ponds, as far as their shape is concerned. But, clearly, they are hills, for on either side are small streams running away from them. If they were ponds, the stream lines would run toward the closed contours. The test of "hill, valley, hill," will always solve the problem when there are not enough stream lines shown to make evident at once whether a closed contour marks a pond or a hill. Look in the beginning for the stream lines and valleys, and, by contrast, if for no other reason, the hills and ridges at once loom up.

To illustrate the subject of contours to aid those who have difficulty in reading contoured maps the following is suggested:

1. Secure modeling clay and build a mound.

2. Use wire and slice this mound horizontally at equal vertical intervals into zones; then insert vertical dowels through the mound of clay.

3. Remove the top zone, place on paper, and draw outline of the bottom edge. Trim your paper roughly to the outline drawn. Indicate where the holes made by the dowels pierce the paper.

4. Do the above with each zone of your mound.

5. Place these papers in proper order on dowels similarly placed to ones in original mound at, say, 1 inch vertical interval apart. A skeleton mound results.

6. Replace the zones of the clay mound and form the original clay mound along the side of skeleton mound.