460 Scientific Proceedings, Royal Dublin Society. 



Wlience I formulated the axiom, never sufficientlj repeated, be- 

 cause it is the basis of the new architectonic precepts preservative 

 against the action of earthquakes — The shock communicated to a line 

 of fracture is folloioed by the transverse oscillation of its sides or 

 margins.''^ 



Serpieri took advantage of the great earthquake of 12th March, 

 1873, to thoroughly control the observations of De Rossi, and the 

 result was the most complete confirmation of the laws established 

 by De Eossi on the propagation of earthquakes by the fractures 

 with waves parallel and normal to the axis of the systems of frac- 

 ture. 



This earthquake of 12th March, 1873, was mapped by Captain^ 

 Gatta, and from this map there resulted " that the central zone 

 coincided with a long lineal tract of the axial crest of the Apen- 

 nines, and that the arrows (of direction of wave) parting all from 

 this crest, assumed directions along the two slopes parallel to the 

 axes of all the valleys of the rivers. It is a most notable thing 

 that nearly all the valleys of the Apennines are thus shown to be 

 geological fissures dividing the masses of the mountain chain." 



Further on he says : " The fissures of the earth wherever met 

 with represent a series of obscisses and ordinates. It is clear that 

 where the seismical agent breaks out it should propagate itself 

 with greatest violence and rapidity in the direction of the fissure 

 that it penetrates." Thence it propagates itself into the lateral 

 fissures, which thus become derived or secondary radiants. So that 

 in some sort the zone aflPected presents somewhat the appearance of 

 the backbone of a fish with the spines, " round which if a peri- 

 meter be traced it assumes the form of an ellipsis." 



" My map (p. 8), although very imperfect, shows a system of 

 coincidences between the geological fissures and the seismical radi- 

 ants which cannot be fortuitous, and which, therefore, is in itself a 

 demonstration of its scientific truth." 



" It has been already shown that my seismical map is equivalent 

 to a map of the geological fractures or fissures ; but it may be observed 

 that it is at the same time in some sort a hydrographical map of 

 Italy. Whence it follows that the main lines of the geological 

 and orographical structure of Italy, of its hydrography and its 

 seismical lines of works, become identified, or at least are brought 

 into very close connexion." 



