7 i8 SCIENCE PROGRESS 



British Association. These reports are not entirely the work 

 of the late secretary, for Milne always welcomed the co- 

 operation of other members of the committee ; but the 

 portions of chief and abiding interest are those in which he 

 determined the origins of the sixty or more world-shaking 

 earthquakes recorded every year in the observatories associated 

 with the committee. It is one of the most valuable results of 

 recent work that such determinations should be possible whether 

 the earthquakes originate in civilised countries, beneath the 

 ocean, or under lands inhabited by illiterate and wandering 

 tribes. They show that the destructive earthquakes of the 

 world are confined to about a dozen seismic regions, the more 

 important of which lie along the steeply sloping margins of 

 the Pacific Ocean. 



In the physical history of the globe, however, an interval 

 of fourteen years is but as one day. No fact of seismology is 

 more clearly established than the continual migration of seismic 

 activity. From month to month, even from hour to hour, the 

 centre of action ranges along the line or lines of fault which 

 give birth to a series of earthquakes. In larger districts the 

 same displacement occurs over greater distances and at longer 

 intervals of time. Thus the interesting maps which Milne 

 published annually in his reports show only the region in which 

 the earth's crust is being deformed at the present time. In past 

 centuries the seats of chief activity may have been very different. 

 What they were Milne sought to determine in one of his latest 

 contributions to seismology — his " Catalogue of Destructive 

 Earthquakes, a.d. 7 to a.d. 1899." As complete probably as such 

 a catalogue can now be made, it is inevitably defective. The 

 total number of entries in it is 4,151, and many of the earth- 

 quakes recorded in it would fall far short of the intensity of a 

 world-shaking earthquake. Yet if the latter occurred through- 

 out the Christian era at the present rate of sixty a year, the 

 total number would be more than 113,000; that is to say, ninety- 

 six out of every hundred great earthquakes in the past nineteen 

 centuries may remain for ever unknown to us. Nevertheless, 

 Milne's second great catalogue of earthquakes possesses a value 

 that will only be fully known after a careful analysis of its 

 contents has been made. 



From what has been already said it will be obvious that 

 Milne was a student of earthquake phenomena rather than of 



