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LX.— ON DE EOSSI'S SEISMICAL AND ENDODYNAMICAL 

 MAP OP ITALY. By PKOFESSOE J. P. O'EEILLY, 

 C.E., M.K. I. A. 



[Read, May 15, 1885.] 



It would not be too much to say that the particular branch of 

 geology which deals with the forces acting from within the earth's 

 surface, and tending to modify it, has assumed within late years a 

 very great importance ; so much so, that under the name of Seis- 

 mology, Dynamic Greology, Endodynamic Greology, it has attained 

 the rank of a specialty in connexion with Greology, and has led to 

 observations and methods of observation of the very highest inte- 

 rest and importance. In Grermany, in Switzerland, in Italy, in 

 America, and in Japan, societies have been formed mainly for the 

 study of phenomena coming under this head, and certain of their 

 results seem to me well worthy of being more generally made 

 known. 



The full value of the earthquake as a factor in Geology can hardly 

 be considered as having yet reached a clear and distinct recogni- 

 tion. So many things in this phenomenon have to be accounted 

 for, and their systematic observation is attended with such great 

 difficulties, and even dangers, that such incomplete recognition of 

 their importance can easily.be explained. Besides, earthquakes, up 

 to the present at least, can hardly be foreseen, or only exception- 

 ally, as in the case of the neighbourhoods of Vesuvius and Etna, 

 where seismic observatories are established and under the conduct 

 of skilled observers. That there are premonitory indications in 

 nearly every case is to be presumed ; but as regards the great 

 majority of recorded shocks, data of this character are wanting. 

 And yet the consequences of earthquakes are such that the very 

 greatest interest attaches to the correct observation and interpre- 

 tation of the phenomena which precede them, and which, rightly 

 read, are capable of serving as indications of a coming shock. 



Palmieri at Naples, and De Rossi at Rome, have long occu- 



