EFFECTS PKODUCED UPON BUILDINGS. HI 



produced by earthquakes, it appears to us that the houses 

 which lost the greater number of tiles appear to be those 

 with the steepest pitch, and those where the tiles were 

 simply laid upon the roof and not in any manner fastened 

 down. It would seem that destruction of this sort might 

 to a great extent be obviated by giving the roofs a less 

 inchnation and fixing the tiles with nails. It was also 

 noticed that the greatest disturbance amongst the tiles 

 was upon the ridges of the roofs. Destruction of this sort 

 might be overcome by giving especial attention to these 

 portions during the construction of the roof. 



Relative Position of Openings in Walls. — From what 

 has been said about the fractures in the buildings of Tokio 

 it will have been seen that, with but few exceptions, they 

 have all taken place above openings like doorways and 

 windows. If architecture demands that openings like 

 arches should be placed one above another in heavy walls 

 of this kind, as in fig. 17, there will be lines of weakness 

 running through the openings parallel to the dotted lines. 

 As arches are only intended to resist vertical thrusts, 

 special construction must be adopted to make them strong 

 enough to resist horizontal pulls. For instance, a flat 

 arch would offer more resistance to horizontal pulls than 

 an arch put together with ordinary voussoirs, there being 

 in the former case more friction to prevent the component 

 parts sliding over each other. Or again, above each arch 

 an iron girder or wooden lintel might be inserted in the 

 brick or stone arch. It was suggested to me by my col- 

 league, Mr. Perry, that the best form calculated to give a 

 wall uniform strength, would be to build it so that the 

 openings of each tier would occupy alternate positions, 

 that is to say, along lines parallel to the struts and ties of 

 a girder. In this way we should have our materials so 

 arranged that they would offer the same resistance to hori- 



