290 STUDIES FOR STUDENTS 
lem which he set himself and carried to a most successful conclusion 
has been nothing less than the critical examination and cataloguing 
of all well-authenticated records of earthquakes to determine by a 
numerical figure the relative seismicity? upon a uniform scale of each 
earthquake province upon the globe; to prepare a composite map of 
epicenters for each; and, this once accomplished, to examine the 
topography and geology of each district with relation to its seismicity. 
No less than 170,000 separate shocks have thus been studied and 
placed in correspondence with each other. 
His catalogue completed, de Montessus’ first effort was to deter- 
mine the relation of areas of high seismicity to the topographic relief. 
As a result, it is found that the seismic areas are throughout those of 
steepest general slope: 
In general, one may say that of two contiguous regions—for example, the 
two sides of a valley, the two flanks of a mountain chain, or plains and neigh- 
boring heights—the more unstable is that which presents the greater average 
slope, or the greater difference in altitude—that is to say, the greater relief either 
relative or absolute. The reason for this is without doubt that the relief is most 
frequently in consequence of the importance of dislocations; which, be it because 
of their lack of equilibrium, or because of the continuation of the tectonic move- 
ments which have caused them, quite naturally bring about earthquakes more easily. 
The greater number of earthquakes, however, originate beneath 
the sea, and here, similarly, on the steep margins of the great oceanic 
deeps. For example, the scarp on the border of the great Tuscarora 
Deep has been the seat of much the larger number of destructive 
Japanese earthquakes. ‘The vital question of the relation of earth- 
quakes to volcanic activity, a dependence upon which was a quarter 
of a century ago the almost universal belief of geologists, is thus 
answered: 
Finally, while we may cite regions frequently shaken by earthquakes which 
at the same time have very active volcanoes, one should recognize the fact that 
face du globe,” Berichte d. IIten international. Konjerenz zu Strassburg, Beitrage zur 
Geophysik, Erganzungsband 2, 1903, pp. 325-34. 
“Sur l’existence de deux grands cercles d’instabilité séismique maxima,” 
C. R. de? Acad. des Sc. de Paris, Vol. CXXXVI (1903), pp. 1707-9. 
Les tremblements de terre: Géographie séismologique; avec une préface par 
M. A. de Lapparant; pp. v+475, 99 maps and figures, and 3 plates (Paris, 1906). 
A brief account of the work of de Montessus and a list of his papers is given by 
F. M. Bernard (‘‘Erdbeben Studien des Grafen de Montessus de Ballore,’”? Dze 
Erdbebenwarte, 1902, pp. 1-9). 
t This term here implies both frequency and intensity of seismic shocks. 
