Guiseppe Mercalli, 1850-1914, an Italian seismologist, devised the Mercalli intensity scale. The scale measures the intensity and effects of an earthquake - from I to XII - and rates them in terms of human reactions and observations. For example, a magnitude I shake is not felt by all humans, but detected by seismographic instruments. A magnitude XII shake is catastrophic, with rocks moved and objects thrown about. Van Lill's South African Miscellany, Dawid van Lill.

Guiseppe Mercalli, 1850-1914, an Italian seismologist, devised the Mercalli intensity scale. The scale measures the intensity and effects of an earthquake - from I to XII - and rates them in terms of human reactions and observations. For example, a magnitude I shake is not felt by all humans, but detected by seismographic instruments. A magnitude XII shake is catastrophic, with rocks moved and objects thrown about. Van Lill's South African Miscellany, Dawid van Lill.