194 EAETHQUAKES. 



same shock, give directions corresponding to all points of 

 the compass. Much, no doubt, depends upon the situa- 

 tion of the observer, and much, perhaps, upon his tem- 

 perament. If he is sitting in a room alone, and is accus- 

 tomed to making observations on an earthquake, on feeling 

 the earthquake, if he concentrates his attention on the 

 direction in which he is being moved, his observations 

 may be of value. If, however, he is not so situated, and 

 his attention is not thus concentrated, his opinions, unless 

 the motion has been very decided in its character, are 

 usually of but little worth. 



Direction determined from destruction of build- 

 ings. — When an observer first sees a town that has been 

 partially shattered by an earthquake, all appears to be 

 confusion, and it is difficult to imagine that in such ap- 

 parent chaos we are able to discover laws. If, however, 

 we take a general view of this destruction and compare 

 together similarly built buildings, it is possible to dis- 

 cover that similar and similarly situated structures have 

 suffered in a similar manner. By carefully analysing the 

 destruction we are enabled to infer the direction in which 

 the destroying forces have acted. It was chiefly by 

 observing the cracks in buildings, and the direction in 

 I which bodies were overthrown or projected, that Mallet de- 



1 termined the origin of the Neapolitan earthquake. From 



i the observations given in Chapter VII. it would appear 



j that, with destructive earthquakes, walls which are trans- 



I verse to the direction of motion are most likely to be 



I overturned, whilst, with small earthquakes, these walls are 



! the least liable to be fractured. 



I From a critical examination of the general nature of 



the damage done on the buildings of a town, earthquake 



observers have shown that the direction of a shock may 



I often be approximately determined. The direction in 



