DETEKMINATION OF EARTHQUAKE ORIGINS. 189 



to all the important towns, from thirty to one hundred 

 miles distant from Tokio, bundles of postcards. These 

 were entrusted to the local government offices with a 

 request that each week one of these cards would be re- 

 turned to Tokio stating the number of shocks felt. In 

 this way it was quickly discovered that the majority of 

 shakings emanated from the north and east, and seldom, 

 if ever, passed a heavy range of mountains to the south. 

 The barricade of postcards was then extended farther 

 northwards, with the result of surrounding the origin of 

 certain shocks amongst the mountains, whilst ethers were 

 traced to the sea shore. By systematically pursuing 

 earthquakes it was seen that many shocks had their origin 

 beneath the sea — they shook all the places on the north- 

 east coast, but it was seldom that they crossed through 

 the mountains, forming the backbone of the island, to 

 disturb the places on the west coast. 



The actual results obtained in three months by this 

 method of working are shown in the accompanying map, 

 which embraces the northern half of the main island of 

 Nipon and part of Yezo. The shaded portion of the map 

 indicates the mountainous districts, which are traversed 

 by ranges varying in height from about 2,000 and 7,000 

 feet. The dotted lines show the boundaries of the more 

 important groups of earthquakes which were recorded. 



I. is the western boundary of earthquakes, which at 

 places to the eastward are usually felt somewhat severely. 

 Some of these have been felt the most severely at or near 

 Hakodadi, whilst farther south their effects have been 

 weak. Occasionally the greatest effect has been near to 

 Kameishi. Sometimes these earthquakes terminate along 

 the western boundaries of III. or IV., not being able to 

 pass the high range of mountains which separate the plain 

 of Musashi from Kofu. 



