His attention may be called to the triangular shape of the land mass, with its greatest elevation in the west. He may be told that its length is 5,700 and its greatest width 3,000 miles.
Questions may then be asked as follows: Into how many slopes or great drainage systems is the continent divided? Into what ocean do the waters of the long slope flow? Those of the short slope? Locate and give general direction of the continental axis. Trace this from Behring Strait to Isthmus of Panama.
Compare its length with greatest width of continent. Compare length of long slope (2,200 miles) with length of short slope (500 to 700 miles). Which slope has the longer coast-line? Mold in sand and chalk model, showing the two slopes and continental axis. Compare surface of both slopes. Which has the greater area of highlands? Which of plains? Give number and comparative size of lakes. Compare length and direction of rivers on each slope. What is the character of the coasts and harbors? What of the islands? Which slope has the larger inland drainage system? Compare with oceanic drainage system.
Locate highlands of each slope. Give the appearance of the Appalachian Mountain System. Compare with the Rocky Mountain System. What can be learned as to the general formation and altitude of each slope? (Show typical pictures.) What is the effect of altitude upon the surrounding country? What on drainage? What is the effect of large rivers upon plateaus?
Locate great central valley of North America. What two great rivers flow through this valley? Trace the Mississippi River from its source to its mouth. Trace the Mackenzie River in the same way. What separates the Mississippi basin from the Mackenzie basin? From the Saskatchawan basin? Trace lowest line from the mouth of the Mississippi to the mouth of the Mackenzie. Into what does this line divide the continent? (Into two land masses.)
Compare these two. In which is the continental axis? (In the primary land mass.) The secondary land mass is divided by the Appalachian Mountain System into two slopes, of which the eastern is called the Atlantic slope. Compare these slopes. Where do the Appalachian Mountains begin? (In the St. Lawrence basin.) Nearly to what gulf do they extend? (Gulf of Mexico.) What is their direction? What separates the secondary land mass into two parts—northern and southern? (The St. Lawrence River.) The northern part is the peninsula of Labrador. In this part trace the water partings of the Hudson Bay river system.
In the primary land mass two immense mountain ranges extend over 5,000 miles—nearly the entire length of the continent. What are these mountains called? Compare their general altitude with the low range of mountains (100 feet high) crossing the Isthmus of Panama. How wide is this Isthmus? (Fifty miles from coast to coast.)
What is known about a certain canal which has been begun in Panama? Is there any other important canal in Central America?
Commencing in the southern part of Mexico, and extending northerly and westerly, two great ranges bound the great plateau of Mexico on the east and west. This plateau is divided by the Rio Grande, Colorado, and other rivers, at a distance of about 500 miles north. The southern part of it is a volcanic region, in which are Popocatapetl and other high mountains.
What can be told about the Colorado River? (Show pictures of structure, also of ancient cliff dwellings.) What is the character of the rock through which the river cuts? Is it in the region of much rainfall or of no rainfall? North of the great plateau is the great basin, 600 miles wide and 900 miles from north to south, enclosed by the Sierra Nevada, Wasatch and Rocky Mountains.