Petrography lower if wholly or partly vitreous. The specific gravity of the more common rocks range from about 2.5 to 3.2. Archaeologists use petrography to identify mineral components in pottery. This information ties the artifacts to geological areas where the raw materials for the pottery were obtained. In addition to clay, potters often used rock fragments, usually called "temper" or "aplastics", to modify the clay's properties. The geological information obtained from the pottery components provides insight into how potters selected and used local and non-local resources. Archaeologists are able to determine whether pottery found in a particular location was locally produced
What Is History? sometimes been made to treat history as a branch of sociology." About the rise of social history as a subject at the expense of political history, Carr wrote:"Social history is the bedrock. To study the bedrock alone is not enough; and becomes tedious; perhaps this is what happened to Annales. But you can't dispense with it". Through Carr himself had insisted that history was a social science, he regretted the decline of history as a discipline relative to the other social sciences, which he saw as a part of a conservative trend. Carr wrote: "History is preoccupied with fundamental processes