contained pozzolana, a volcanic ash. When the piers reached a height of 30 feet above the river, wooden arches were hoisted into its place between them. A wooden road was nailed to the arches and covered with a layer of earth. The finished road stood over sixty feet above the river. For major or busy bridges sometimes stone went in place of wood. The semicircular arch was usually used for bridges. Aqueducts were like a bridge but built over land and carried pipes of water instead of a roadbed.
             Rome alone needed 340 million gallons of water per day to supply its great arched baths and other needs. Surveyors made an imaginary line with measuring sticks and a chorobate, a leveling instrument like the level used today, to make a straight line for a profile map. The surveyors designed a plan
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