DISTRIBUTION IN SPACE AND TIME. 227 



great earthquakes are the most frequent. The actual 

 number of earthquakes which have been felt in the 

 differently coloured areas are given, when speaking of the 

 relation of seismic energy to season. 



When looking at this chart it must be remembered 

 that if we were to make a detailed map of any one of 

 the different countries where earthquakes are frequent, 

 we should find in it all the differences that we observe in 

 the general chart. For instance, one portion of Japan, 

 where perhaps sixty shocks are felt per year, would be 

 coloured with a dark tint, whilst other portions of the 

 same country, where there is only one slight shaking felt 

 every few years, would be left almost uncoloured. The 

 black dots indicating the position of volcanic vents are 

 even more general in their signification than the tinted 

 areas. Professor Haughton gives for the world a list of 

 407 volcanoes, 225 of which are active. These numbers 

 are the same as those given by A. von Humboldt. Of the 

 active volcanoes 172 are on the margin of the Pacific, 

 and of the total number eight are in Japan. From my own 

 observations in Japan independently of the Kurile Islands, 

 I have enumerated fifty-three volcanoes which are either 

 active or have been active within a recent period. In a 

 few years' time this list will probably be increased. I 

 mention this fact to show how very imperfect our 

 knowledge is respecting the number of volcanic vents 

 existing on our globe. If we were in a position to 

 indicate the volcanoes which had been in eruption during 

 the last 4,000 years, the probability is that they would 

 number several thousands rather than four or five 

 hundred. 



An inspection of the map shows that earthquakes 

 chiefly occur in volcanic and mountainous regions. The 

 most earthquake-shaken regions of the world form the 



