PROBLEM.--By use of the slope scale on the sketch board and the contour interval scale on the alidade, each man will secure vertical data on the flat sketch made in the fourth lesson. Certain critical elevations will be determined and marked with red flags before hand. The elevations of two points on the ground will be furnished, one as the datum and the other as a check. Draw in contours of this sketch with the help of drainage lines and elevations already secured. The chief points to be considered are to take slopes from points established on the sketch; to take several sights and average the angle of slope; to properly lay off the elevation by using the slope scale on the alidade; and finally to put in the contours along these lines of sight _on the spot_ thus allowing for difference in topography between the point of sight and the station from which the elevation is taken. Careful note must be made of the drainage systems as these are the keynotes to the sketch and finally the contours are connected together, keeping in mind always that no contour stops unless it makes a closed curve or goes off the map. Remember also that contours make fingers pointing up stream and are blunt around hill sides. Contours cross streams to opposite points and break at roads, continuing on the other side. Uniform slopes have equally-spaced contours. Do not try to measure every slope, two intersecting elevation sights on a hill will check the height. Put the intervening contours in by eye. LESSON 7. (CLASSROOM--FOUR HOURS.) PROBLEM.--Completing the map sketch previously made and making a landscape sketch. It is important to complete a map and no matter how good it is, if certain points are omitted, the value of the work is very much decreased. The sketcher must clear the sketch of all unnecessary lines and notes and make his lettering clear on the map. Be sure that the following items are on the sketch before it is turned in. 1. Location of the ground shown. 2. Line of magnetic north shown by an arrow, and if declination is known, the true north also. 3. Graphic scale and representative fraction--R.F. 4. Vertical interval--V.I. 5. Sketcher's name and organization to which he belongs. 6. Date.