EFFECTS PKODUCED UPON BUILDINGS. 103 



The results showed that, in order to avoid the effects 

 of small shocks, all walls containing principal openings 

 should be placed as nearly as possible at right angles to 

 the direction in which the shocks of the districts usually 

 travel. The blank walls, or those containing unimportant 

 openings, would then be parallel to the direction of the 

 shocks — that is, presuming our building to be made up of 

 two sets of walls at right angles to each other. 



Another point of importance would be to build arch- 

 ways curving into the supporting buttresses ; the archways 

 over doors and windows which we find in earthquake 

 countries do not appear to be in any way different from 

 those which are built in countries free from earthquakes. 

 In the one country these structures have simply to with- 

 stand vertical pressures applied statically ; in the other, 

 they have to withstand more or less horizontal stresses, 

 applied suddenly. 



Relation of Destruction to Earthquake Motion, — The 

 relations which exist between the overturning and pro- 

 jection of bodies and the motion of the ground have 

 already been discussed. It may be interesting to call 

 attention to the fact that in the formulae showing three 

 relationships, it was the shape rather than the weight 

 of a body which determined whether it should be over- 

 turned or projected by a motion at its base. 



As an interesting proof that light bodies may be over- 

 turned as easily as heavy ones, Mallet refers to the over- 

 turning of several large haystacks as one of the results 

 of the Neapolitan earthquake. 



If masses of material are displaced or fractured, then 

 Mallet remarks that the maximum velocity will exceed 

 ^/2gk, where h is the amplitude of the wave. Should the 

 maximum velocity be less than this quantity, the masses 

 which are acted upon will be simply raised and lowered, 

 6 



