Figure 5 is a drawing of the slab in Figure 4 but now there is a loaded cart halfway across the slab and the slab has deformed into a curve under the influence of the weight of the cart. The slab is sagging under the weight of the cart. Included in the illustration is a magnified view of the slab under the cart. In this magnified view, two pairs of arrows have been drawn on the slab. In the upper half of the slab the arrows are pointing towards each other indicating the presence of compression forces and that the top half of the slab is in compression. In the lower half of the slab the arrows are shown pointing away from each other indicating the presence of tension forces and that the bottom half of the slab is in tension.

 1.2.1 The Pont du Gard: one of a kind