116 CHARLES DAVISON 
Of these zones, Nos. 1-4 lie on the northern half, and Nos. 6-10 
on the southern half, of the volcano. 
As in the Etnean region, there is at present no apparent law 
in the transference of the epicenters from one zone to another. 
The nature of that transference may be shown by a brief reference 
to the more important earthquakes of the last forty years. On 
September 2, 1883, an earthquake of intensity 7 (Mercalli scale) 
Colonna 
Genazzano 
° 
Frascati © O M.Compatri 
2 Grotti ferrata 
palms SS fauee ai papel 
Castel eget ° Se 
Albano © Bim 
Ariccia 2 
Genzano 
Velletri 
Civitalavinia © ° 
Scale of Miles 
Fic. 7.—Map of Albano earthquake of February 21, 1906 
caused slight damage at Frascati, Grottaferrata, Rocca di Papa, 
and Monte Cavo (zone 4), the axis of the area of maximum inten- 
sity being directed southeast or along a radius from the summit 
of Monte Cavo; on January 17, 1886, there was a very strong 
shock at Ariccia (zone 7); on January 22, 1892, a shock with its 
epicenter between Genzano and Civitalavinia (zone 10); on May 
8, 1897, a strong shock without damage at Colonna, the axis of 
the area of maximum intensity being directed southwest or along 
a radius (zone 1); on November 6, 1897, a shock at Civitalavinia 
