50 NINTH REPORT. 



the winter months of 1905-06 to a survey of Cala])rian earthquake records 

 for the last three centuries, and for ]5urposes of comparison large scale maps 

 were prepared to show the distribution of damage from each earthquake in- 

 dividually. The result has been a confirmation of the working hypothesis, 

 for the lines of damage indicated by one earthquake have been found to be 

 those of the others as well, save only that the heavier disturbances have cor-' 

 responded to- movement also on certain additional fracture lines. It was 

 with considerable satisfaction that I found in the records of the great earth- 

 quake of 1783 a statement that the initial shock had leveled the buildings 

 along the Strada di Forgiari in Monteleone but had not affected the other 

 buildings of the city. Unlike strokes of lightning, .therefore, earthquakes 

 appear to search out the same places for their repeated attacks. From these 

 Calabrian studies we may conclude that at the time of earthquake shocks 

 opportunities for learning important facts are afforded which at other times 

 are denied to us. The earth's surface is at the time of an earthquake, so to 

 speak, sensitized to reveal its hidden architecture, much as are our bodies 

 imder the influence of the x-ra3^s or the fluorescent screen. 



An additional fact of importance foreshadowed upon the staff map of 

 Gen. Ferrario was that the points of intersection of the lines of special dam- 

 age had received much the heaviest shocks. Without appreciating its sig- 

 nificance this fact has been unconsciously recognized in Italy by those officers 

 whose duty it has been to receive and classify the reports of damage from 

 earthquakes. When an earthquake has been announced in a definite ])rov- 

 ince of the Italian peninsula, men familiar with the earthquake history of the 

 district can tell in advance what communes will probably report damage 

 and what others will have been immune. It is, in fact, wholly possible upon 

 the basis of reports now upon record to derive numerical figures which, in a 

 relative scale, set forth the danger from earthquake shocks of each commune 

 in Itialy. 



The lines of special damage from earthquakes — the so-called seismotec- 

 tonic lines — are found to be in most cases the generally rectilinear features 

 upon the surface, as, for example the borders of plateaus, the bluffs along 

 the coast, the boundaries of geological formations, the sharp lines of drainage, 

 or, perhaps, the line joining waterfalls in neighboring streams; but in any event 

 lines relatively straight and technically described as lineaments. 



When the Calabrian studies just referred to had been completed there ap- 

 peared the great work of the Count de Montessus upon Seismic Geography. 

 By a method of compiling and standardizing, so to speak, all the earthquake 

 records within each earthquake province of the globe, de Montessus has pre- 

 pared a series of maps which, speaking broadly, show the distribution of dan- 

 ger from earthquakes within each of these provinces. The results are the 

 more reliable in those provinces where careful records have been longest 

 preserved, but collectively they possess a value which, in view of the pains- 

 taking statistical researches upon which they are based, it would be difficult 

 to overestimate. Examining now these maps with reference to the linea- 

 ments of the surface, it was a special satisfaction to find that with hardly an 

 exception they show the special danger spots to lie at intersections of the 

 prominent features within each district. Two maps may be chosen by way 

 of illustration — the northern section of the British Islands and the Greater 

 Antilles. In both these cases the earthc^uake danger spots are ranged upon 

 the lineaments, with the places of special seismic prominence located at their 

 intersections. 



We may now come nearer home and survey for a moment an earthquake 



