[Illustration]
Take your pencil and draw an outline of this state, then a line from
Chicago to Rock Island, from Rock Island to East St. Louis, from East
St. Louis to Springfield and from Springfield back to Chicago. Notice
that the line connecting these cities forms a triangle. Get the visual
impression of the triangle in mind. Now close your eyes and see if you
can see the outline of the state clearly and upon it the line joining
the principal cities.