EFFECTS PRODUCED UPON BUILDINGS. 145 



5. Avoid the edges of scarps or bluffs, both above and 

 below. 



6. So arrange the openings in a wall, that for horizontal 

 stresses the wall shall be of equal strength for all sections 

 at right angles. 



7. Place lintels over flat arches of brick or stone. 



8. To withstand destructive shocks either rigidly 

 follow one or other of the two systems of constructing an 

 earthquake-proof building. The light building on loose 

 foundations is the cheaper and probably the better. 



9. Let all portions of a building have their natural 

 periods of vibration nearly equal. 



10. If it is a necessity that one portion of a building 

 should have a very different period of vibration to the 

 remainder, as for instance a brick chimney in a wooden 

 house, it would seem advisable either to let these two 

 portions be sufficiently free to have an independent 

 motion, or else they must be bound together with great 

 strength. 



11. Avoid heavy topped roofs and chimneys. If the 

 foundations were free the roof might be heavy. 



12. In brick or stone work use good cement. 



13. Let archways curve into their abutments. 



14. Let roofs have a low pitch, and the tiles, especially 

 those upon the ridges, be well secured. 



