Slate roofs have been used throughout human history because of the durability and longevity of this material. Slate is derived from shale sediment composed of clay or volcanic ash. Its breakability and its toughness both make it easy to partition into thin but durable sheets. However, quarrying and transporting it was a dangerous and laborious process. Typically, it was dug out of the ground with hand tools, then moved by horse and wagon. When the Romans