STUDIES LOR, SHOP ENZS 
THE RECENT ADVANCE IN SEISMOLOGY 
WILLIAM HERBERT HOBBS 
University of Michigan 
I. THE DISTRIBUTION OF SEISMICITY IN RELATION TO THE 
EARTH’S MOBILE BELTS 
Introduction.—It is entirely safe to say that no period of equal 
length has registered so great an advance in the science of seismology 
as the decade now just brought to a close. The more important 
developments of this period may be broadly stated under three heads: 
(1) the determination of the laws of distribution of seismicity; (2) 
the discovery of a method for sensing and locating macroseisms 
through the body of the planet; and (3) the accumulation of so large 
a body of observational data as to advance from the condition of 
vague speculation to a well-grounded theory of the cause of earth- 
quakes. 
The laws of distribution of seismicity have been determined by ~ 
a French officer of artillery, Count de Montessus de Ballore, whose 
thorough and conscientious work has occupied almost a lifetime. 
Rudolph had already, in 1887, made a most important contribu- 
tion to the subject in a series of papers upon the distribution 
of seaquakes and submarine volcanic eruptions, which are supple- 
mentary -to the studies by de Montessus. The discovery of new 
methods for studying at a distance the greater world-shakings is 
to be attributed, perhaps more than to anyone else, to the veteran 
English seismologist, Professor John Milne, who first started the great 
movement in Japan for seismological investigation, and since his 
return to England has been generously supported by the British 
Association for the Advancement of Science. The most modern 
and thoroughly equipped earthquake station today is, how- 
ever, the German Chief Station for Earthquake Investigation at 
Strassburg, long directed by Professor Gerland, the founder of the 
International Seismological Association and the editor of its admirable 
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