Washington — Catalan Volcanoes and their Rocks. 219 



noes being omitted, so that the map leav r es much to be desired. 

 It is probably on this that the sketch map mentioned by Sapper 

 is based, of which I was unable to obtain a copy, and it also 

 serves as the basis for the map on the same scale given by 

 Gelabert, on which the positions of the volcanoes are roughly 

 indicated. A sketch map of the district is given in fig. 1, 

 based on the map mentioned above. Only the more prominent 

 volcanic cones are shown (by small circles), and the railroad, 

 which extends from Gerona to San Feliu, is omitted. 



I would take this opportunity to express my thanks to Senores 

 Calderon and Fernandez Navarro for courtesies and assistance 

 shown me in Madrid preparatory to my visit to Olot. 



Topography and Geology. 



Prevolcanic Geology. — The volcanoes which form the subject 

 of the present paper are situated in the modern Province of 

 Gerona (embraced within the ancient Catalonia), in north- 

 eastern Spain, between the eastern end of the Pyrenees on the 

 north and the Sierra de Monseny on the south. The area 

 occupied by them is part of the Eocene gulf which extended par- 

 tially across northern Spain from the Gulf of Lyons, the vol- 

 canic area proper occupying the site of a Pliocene bay, which 

 formed the last filled and most eastern part of this. The chief 

 sedimentaries of the district are nummulitic limestones of 

 Eocene age, with some later conglomerates, and a small patch 

 of Silurian shales and limestones near Llora, along the Rio Ter. 

 These earlier rocks are quite variable in dip and strike, and 

 faulting is common in the Eocene limestones. The fault scarps 

 thus produced are quite prominent features in the topography, 

 being often several hundred feet in height. From such obser- 

 vations as I made, it seemed that the area is one of faulted 

 blocks, the dips being in diverse directions and usually at 

 rather low angles, seldom over 25°, though I was able to de- 

 vote so little time to this phase of the geology that I cannot 

 speak decisively on the subject. 



In the depressions and fault valleys thus formed were laid 

 down thin deposits of Quaternary sands, clays, and conglom- 

 erates, which, with the Tertiary strata, underwent very consider- 

 able erosion prior to the beginning of the volcanic activity. 



It wo aid seem that there was some feeble vulcanicity mani- 

 fested in the Tertiary,* but the era of the volcanoes which 

 interests us here began about the middle of the Quaternary, 

 and continued into the present period, as is evident from the 

 excellent state of preservation of the volcanic cones, though 

 there is no historic record of any eruptions. The influence of 

 *Cf. S. Calderon, Bol. Soc. esp. Hist. Nat., 1905, p. 340. 



