466 Notices of Memoirs — Earthquake Phenomena in Japan. 



4. The Overhirning and Fracturing of Columns, Walls, etc. 



By continuing experiments on the overturning of columns when 

 subjected to eartliquake-like motion, we can now state with con- 

 fidence the acceleration required to overturn any given column by 

 its own inertia. In the experiments on fracturing, all the brick 

 columns and walls snapped at their base. The form of column 

 which when moved back and forth by an Earthquake will offer an 

 equal resistance at all horizontal sections to the effects of its own 

 inertia has been determined. 



In ordinary engineering practice the cross- section of piers is 

 practically uniform from the base upwards — short piers near a river 

 bank have the same ci'oss-section as long piers in the centre of the 

 river, etc. A large series of piers for bridges now being built in 

 Japan have been designed in accordance with the rules resulting 

 from our experiments on fracturing. 



5. The Great Earthquake of October 28th, 1891. 



9,960 people were killed, 128,750 dwelling houses were totally 

 destroyed, and in a few seconds Japan lost the equivalent of perhaps 

 30 million dollars. About twelve million dollars have already 

 been poured into the district for repairs and relief. The movement 

 reached Berlin at the rate of 9,800 feet per second. At Tokyo, 

 150 miles from the origin, the ground moved in long flat waves, 

 which tilted the water in ponds and caused seismographs to act as 

 angle measurers. These waves had a velocity of about eight feet 

 per second. A few chimneys fell. 



The origin was the formation of a fault which can be traced for 

 40 or 50 miles along the surface. Some 3,000 shocks have been 

 recorded since the first great shock. Mountain slopes have been 

 stripped by land slips, valleys are dammed up and lakes have 

 been formed. Valleys have been compressed so that farms have 

 decreased in area. 400 miles of river banks were shaken down 

 or deeply crevassed. Mud volcanoes formed. Eailway lines and 

 bridges twisted and distorted. Foundations of bridges in one case 

 were shifted 19 feet. 



Some thousands of calculations respecting accelerations to produce 

 fracturing and overturning have been made. Records of seismo- 

 graphs have been examined and the velocity of gravity and of elastic 

 waves have been computed. The origin was in a non-volcanic 

 district but where elevation was in progress. Earthquakes seldom 

 originate from volcanoes, but they occur in volcanic countries where 

 secular movements are in progress or where mountains are in process 

 of formation. 



A photographic record taken at each end of a water level several 

 miles in length and if possible at right angles to an axis of elevation 

 might give measurements of slow tilting and throw light on a possible 

 relationship between Earthquakes and these movements, etc. Such 

 an experiment might cost £500. 



Earthquake and Volcanic effects will, if possible, be illustrated by 

 some very large photographs kindly lent by Prof. W. K. Barton, 



