Figure 3 consists of a pair of illustrations, one above the other, and each illustration consists of a cartoon and below it a diagram. All four images contain a rectangle which is approximately 8 times longer than its height. The rectangle is being used to represent any solid object.

In the top illustration, the cartoon shows two people attempting to pull the rectangle away from each other, rather like a tug of war. The rectangle is being put under tension. In the diagram below this cartoon, each person is replaced by an arrow pointing away from the rectangle. Each arrow has a letter F next to it. The letter denotes force and so the arrows are being used to show the force that the people are creating. The two arrows are pointing away from each other, indicating that they are forces that are creating tension in the rectangle.

In the bottom illustration, the cartoon shows two people attempting to push the rectangle towards each other. The rectangle is being put under compression. In the diagram below this cartoon, each person is replaced by an arrow, this time pointing towards the rectangle. Each arrow has a letter F next to it. Once again, the letter denotes force and so the arrows are being used to show the force that the people are creating. In this case, the two arrows are pointing towards each other, indicating that they are forces that are creating compression in the rectangle.

1.2.1 The Pont du Gard: one of a kind