33 - Transportation.

Transportation.  Roads.  The Romans primarily built roads for their military. Their economic importance was probably also significant, although wagon traffic was often banned from the roads to preserve their military value. In total, more than 400,000 kilometres (250,000 mi) of roads were constructed, 80,500 kilometres (50,000 mi) of which were stone-paved.  Way stations providing refreshments were maintained by the government at regular intervals along the roads. A separate system of changing stations for official and private couriers was also maintained. This allowed a dispatch to travel a maximum of 800 kilometres (500 mi) in 24 hours by using a relay of horses.  The roads were constructed by digging a pit along the length of the intended course, often to bedrock. The pit was first filled with rocks, gravel or sand and then a layer of concrete. Finally, they were paved with polygonal rock slabs. Roman roads are considered the most advanced roads built until the early 19th century. Bridges were constructed over waterways. The roads were resistant to floods and other environmental hazards. After the fall of the Roman Empire the roads were still usable and used for more than 1000 years.  Most Roman cities were shaped like a square. There were 4 main roads leading to the center of the city, or forum. They formed a cross shape, and each point on the edge of the cross was a gateway into the city. Connecting to these main roads were smaller roads, the streets where people lived.  Bridges.  Roman bridges were built with stone and/or concrete and utilized the arch. Built in 142 BC, the Pons Aemilius, later named Ponte Rotto (broken bridge), is the oldest Roman stone bridge in Rome. The biggest Roman bridge was Trajan's Bridge over the lower Danube, constructed by Apollodorus of Damascus, which remained for over a millennium the longest bridge to have been built both in terms of overall and span length. They were most of the time at least 60 feet (18 m) above the body of water.  Carts.  Roman carts had many purposes and came in a variety of forms. Freight carts were used to transport goods. Barrel carts were used to transport liquids. The carts had large cylindrical barrels laid horizontally with their tops facing forward. For transporting building materials, such as sand or soil, the Romans used carts with high walls. Public transportation carts were also in use with some designed with sleeping accommodations for up to six people.  The Romans developed a railed cargo system for transporting heavy loads. The rails consisted of grooves embedded into existing stone roadways. The carts used in such a system had large block axles and wooden wheels with metal casings.  Carts also had brakes and elastic suspensions. The elastic suspension systems used leather belts attached to bronze supports to suspend the carriages above the axles. The system helped to create a smoother ride by reducing vibration. The Romans adopted bearings developed by the Celts. The bearings decreased rotational friction by using mud to lubricate stone rings.  Industry.  Mining.  The Romans also made great use of aqueducts in their extensive mining operations across the empire, some sites such as Las Medulas in north-west Spain having at least 7 major channels entering the minehead. Other sites such as Dolaucothi in south Wales was fed by at least five leats, all leading to reservoirs and tanks or cisterns high above the present opencast. The water was used for hydraulic mining, where streams or waves of water are released onto the hillside, first to reveal any gold-bearing ore, and then to work the ore itself. Rock debris could be sluiced away by hushing, and the water also used to douse fires created to break down the hard rock and veins, a method known as fire-setting.  Alluvial gold deposits could be worked and the gold extracted without needing to crush the ore. Washing tables were fitted below the tanks to collect the gold-dust and any nuggets present. Vein gold needed crushing, and they probably used crushing or stamp mills worked by waterwheels to comminute the hard ore before washing. Large quantities of water were also needed in deep mining to remove waste debris and power primitive machines, as well as for washing the crushed ore. Pliny the Elder provides a detailed description of gold mining in book XXXIII of his Naturalis Historia, most of which has been confirmed by archaeology. That they used water mills on a large scale elsewhere is attested by the flour mills at Barbegal in southern France, and on the Janiculum in Rome. Wikipedia: Text is available under the Creative Commons Attribution-ShareAlike 4.0 License.This episode includes AI-generated content.