A little boy wanted to show his cousin, who lived some miles away; the shape and size of his house, and how the rooms were arranged. How could he do this?

On a large sheet of white paper, he placed lines of blocks in the form of his house. Then, with a lead pencil, he drew a line on the paper along the sides of the blocks. He next took up the blocks, and there, on the paper, was a plan of his house.

Here is a picture of a schoolroom. We see desks, the teacher's table, a chair, a clock, globe, and two maps, in the picture. The picture shows these objects as they would appear if we stood at the door behind the 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.

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.

And lastly, we will draw a circle for the globe, and an oblong and square for the teacher's table and chair, that shall show just where and just how long these objects are.

We have now a plan  of the schoolroom. Let us put N. to show the north side of the room, S. to show the south side, E. to show the east side, and W. to show the west side. We can now tell the direction of one thing from another in our plan.