168 



KNOWLEDGE. 



May, 1913. 



lower ones, the vibration being greater at a height 

 than at the base. Again, a structure may be very 

 heavy, but if built of bad material it can have no 



Figure 153. The Earthquake- proof Building erected in 

 the grounds of the Imperial University, Tokyo. 



resisting power, and it will simply " smash down," 

 for good material and good construction are more 

 important than thickness of walls. Now, in the 

 Punjab the houses were built solidly enough, the 

 walls being two feet thick, but they were tilled up 

 with rubble and small stones, and were, therefore, bad 

 from an earthquake point of view. 



Professor Omori speaks very decidedly with regard 

 to the responsibility of Government in the erection 

 of jails and barracks, and he used a stronger expres- 

 sion than the writer ever heard before on the lips of 

 a Japanese in criticising Occidental methods, when 

 he said, in conclusion: " It is almost criminal on the 

 part of the Government to build bad structures for 

 public purposes, such as schools, jails and barracks, 

 and my advice to the Indian Government would be 

 to build more substantially, always on a sure foun- 

 dation, with good binding either of wood or iron, and 

 to use good material, especially in the case of public 

 buildings." 



In Calcutta, Professor Omori found that the 

 theory of the engineers was, that the soft soil of 

 Calcutta acted as an elastic cushion, and, by absorb- 

 ing the earthquake motion, prevented it from being 

 communicated to structures standing upon it. Now 

 this was quite an erroneous idea, earthquake motion 

 being invariably felt more in soft than hard ground ; 

 and even within the confines of the city of Tokyo a 

 shock varies considerably, one in the upper part 

 being one-half less in intensity than it is in the 

 lower and softer parts. The same fact was also 

 made evident in San Francisco, where at the time 

 of the earthquake " made ground " and soft land 

 suffered more than the hard. 



Speaking generally, the most important principle 

 in construction is to make the structure a single 

 body, simple and compact, avoiding the possibility 



of different parts assuming different movements or 

 vibrations. For example, chimneys are dangerous, 

 because a chimney vibrates differently from the 

 main building, and in the event of earthquake it 

 will be found that a chimney is always broken at its 

 junction with the roof : so that, as the fracture of a 

 brick column occurs at a joint, its seismic stability 

 ought to be increased by using good mortar, until 

 the strength of the joint becomes equal to that of 

 the bricks themselves. In 1894 a curious earthquake 

 occurred in Tokyo, during which several chimneys 

 were knocked down in barracks, factories, and 

 schools, killing many soldiers and others. To 

 obviate this danger the Japanese now make the part 

 above the roof of light material, such as sheet-iron, 

 or better still, of earthenware (dokwari). As a 

 matter of fact, Tokyo is rendered generally hideous 

 by these iron chimneys — perfect abominations, 

 which tower above the roof-line, and are, indeed, 

 made so long that, when they fall, they do not crash 

 through the roof, but topple over into the street or 

 garden beyond. 



In Japan, it is interesting to note that ancient 

 castle walls, built several hundreds of years ago, 

 have forms approximately equal to the curve theor- 

 etically giving the greatest stability against earth- 

 quake, known geometrically as the parabolic curve. 

 We find that the walls of all old castles are made of 

 parabolic section, thicker at the base, in the form 

 which mathematicallvgives uniform strength through- 

 out the height and prevents the formation of cracks ; 

 and, as a matter of fact, all these castles have with- 

 stood terrific shocks of earthquake. 



There is no better example in the whole country 

 than the walls of Nagoya Castle (see Figure 154), 

 which are built of polygonal blocks, ten, twenty or 



Figure 154. Nagoya Castle, one of the "sights of Japan." 



The walls are of parabolic sections, to give stability against 



earthquakes. 



thirty feet long, uncemented, and fitted into the 

 bank at an even slope ; and yet, after hundreds of 

 years of storm and earthquake, there is scarcely a 



