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MAP OF NORTH AMERICA.
It is supposed that in the course of their study, the pupils have been in the habit of modeling in sand and chalk modeling on the blackboard at every step of the way. It may now be found that they are prepared to represent the entire continent, first in two slopes, again in land masses, and then as an aggregation of river basins, as suggested in the last lesson.
Such a development of the map is illustrated in the present lesson by four stages of chalk modeling. The first stage is represented in [Fig. 61]. It shows the continent of North America in two great slopes, one long one sloping to the east, and a short one sloping to the west, from the line of meeting of their upper edges, or what has been termed the Continental Axis.
[Fig. 62] represents the continent as sketched after a study of it as simple land masses—a primary land mass, and a secondary land mass, with the line of depression at the meeting of the two opposing slopes. This line is indicated by lines slanting downwards towards the depressed axis.
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