teacher's table and looked in.

This is a plan of the schoolroom, a picture of which is shown above.
You see, the plan and picture are quite different.

[Illustration: "THE PLAN SHOWS WHERE THE OBJECTS ARE."]

The picture shows the objects as we see them before us. The plan shows
where the objects are, and their direction from one another.

Now let us see if we can make a plan of the same schoolroom on the
blackboard.

The first thing is to measure the sides of the room. We will suppose the
two long sides are each forty feet long, and the two short sides each
thirty feet long. Now we will draw four straight lines on the board for
the four sides. Of course, the lines must be much shorter than the sides
themselves, else our plan will be too large.

Make one inch in the plan stand for one foot in the room. So the lines
for the long sides will each be forty inches long, and the lines for the
short sides thirty inches long.

The next thing is to make spaces in the sides for the door and the
windows, and oblongs for the desks. But we must remember that an inch in
our plan stands for a foot in the object itself, and therefore we must
allow as many inches for the width of doors and windows, and for the
length and width of the desks, as there are feet in the objects
themselves. Thus, if the door is three feet wide, we must make it three
inches wide in our plan.