EARTHQUAKE IN THE MAESICA — MANCINI. 217 



the earthquake of January 13 is on this line and does not coincide 

 with any other seismic locality. However, Dr. Martinelli, who has 

 gone over with great care the seismic history of the regions traversed 

 by tlie axial line of Prof. Omori, thinks that it is merely a curious 

 coincidence; in fact, in tracing this line Prof. Omori has not con- 

 sidered other important earthquakes, which would have altered the 

 direction of it. 



The seismogram recorded by Agamennone's seismograph with 

 horizontal pendulums is remarkable for its amplitude. The regis- 

 tering apparatus of the Bureau at Rome, except for the presence of 

 lateral stop screws, would have been put out of action by the shock, as 

 happened to the seismograph of the Observatory of Rocca di Papa. 

 The great seismograph of Strassburg was dismounted by the vio- 

 lence of the shock, and the passage of the seismic waves was recorded 

 by all the sensitive seismographic instruments in the world, even to 

 Japan, Australia, and Canada. The seismogram shown here (fig. 

 3) is that traced by a bifilar pendulum at the Seismologic Observa- 

 tory of Cartuja, in Granada ; at P and S are shown the beginnings 

 of the preliminary quakes. 



The shock commenced at exactly 7h. .52m. 558. in the direction 

 E. 6° jST., the direction from Rome to the region affected by the dis- 

 aster. During that day and in the days following several small 

 repetitions of the iDhenomenon were noticed. Concerning these repe- 

 titions. Prof. Agamennone observed on the instruments of the 

 Geodynamic Observatory of Rocca di Papa, up to the Gth of Feb- 

 ruary, 750 shocks, occurring sometimes at intervals of less than a 

 minute apart, revealing the state of continual convulsions of the 

 earth in the epicentral area. 



The position of the epicenter of the earthquake has not yet been 

 exactly established. This uncertainty and the enormity of the devas- 

 tation wrought in the Valley of the Liri have led Agamennone to 

 believe in the existence not of a single center but of two separate 

 seismic centers which came into action cither at the same instant or 

 one immediately following the other, as occurs in earthquakes spoken 

 of as " in relays." It might even be that the epicenter had a linear 

 form of considerable length and for reasons of a geologic nature the 

 devastation was manifested in two widely separated localities. 



From the preliminary researches carried on by Prof. Oddone on the 

 sites of the disaster, relating to the details of the seismic waves, to 

 their transmission, speed, height, etc., it would seem that it can already 

 be deduced that the complete period of the waves was 0.7 second, the 

 length of the waves from summit to summit about 20 meters, with a 

 height of 20 centimeters. The mean speed of transmission, according 

 to Agamennone, appeared to be about 7.69 meters per second. The 

 bulging movement of the ground caused the destruction of the walls 



