Proceedings. 63 



and the Peninsula of Kamtschatka, are also liable to these 

 convulsions. The seaboard is not, however, the only district 

 liable to earthquakes. Persia, India (more especially the 

 northern part), and the district known as Central Asia, are 

 subject to violent earth-disturbances, extending evea so far 

 as Eastern Siberia. 



The mischief done by an earthquake is not always to be 

 measured by the violence of the shock. There are shocks of 

 different kinds, chiefly four kinds — tremulous, uudulatiug, 

 upheaving, and rotatory. 



The tremulous shocks appear to be the least destructive. 

 They are common along the Pacific coasts of South America. 

 They usually pass away quickly, but sometimes last for several 

 days. In 1816 the town of Sciaca, in Sicily, was shaken for 

 several days by tremulous shocks. The tremor resembles a 

 heavily-laden wagon passing over a hard, rough, and rocky 

 roadway. 



The undulating shocks are much more destructive. The 

 ground moves horizontally backwards and forwards, and the 

 motion of the earth not being readily communicated to tall 

 buildings, they totter and fall. This undulating motion 

 produces what are termed smart shocks. 



Upheaving shocks are still more disastrous, and are greatly 

 to be dreaded. The force opens the surface of the earth, 

 making chasms sufficiently wide to engulf men, animals, 

 furniture, and houses. Such appears to have been the kind 

 of shock in the great earthquake of Calabria on 28th March, 

 1783. The ground was seen to rise and fall rapidly. Persons 

 were raised from the ground, and thrown to some distance ; 

 houses were removed from their site, and carried to higher 

 elevations. In S. America, after the great earthquake of 

 Riobamba in 1797, corpses were found on the top of a hill 

 several hundred feet higher than the city whence they had 

 been shot by the violence of the concussion, at least so it is 

 reported. Upheaving shocks are almost always accompanied 

 by an undulatory motion, hence to some extent is the increased 

 danger of these convulsions. 



Rotatory shocks are the most destructive of all, but they 



