Washington — Catalan Volcanoes and their Rocks. 221 



is made up of several series of curved prisms, which Carez 

 refers to five separate flows, though they seemed to me to be 

 parts of but one thick flow, the apparent superposition of the 

 series of columns being due to local variations in the conditions 

 of cooling. This rests over the greater part of its area on a 

 thin stratum of loose, scoriaceous material, which lies from 18 

 to 25 meters above the river level. Below this the lava is 

 decidedly platy, rather than columnar, though even this 

 assumes in places a distinctly columnar structure, the prisms 

 being thin and often radiating. The base of this is difficult 

 to see, owing to the abundant talus, which contains, by the 

 way, many fragments of Roman glass, but it is distinctly seen 

 in places to rest upon Quaternary gravels, but little above the 

 water level. The small " basalt hill " mentioned by Sapper and 

 marked on his map, which lies a short distance to the east of 

 the tip of the tongue, across the brook, is evidently an integral 

 part of the main flow, as it shows the same succession of pris- 

 matic and platy lavas separated by a thin scoriaceous layer. 

 In this case the River Fluvia, and the small tributary from the 

 south, have carved channels between the lava flow and the 

 limestone. A photograph of this flow is reproduced in fig. 2. 



Other excellent examples of basaltic columns are shown in 

 the same flow north of La Garrinada, along the small Rio 

 Ridaura, where the stream has cut into the lava itself, and in 

 places has formed deep pot-holes, as well as in the first flow 

 mentioned above near Sellent, and in that from Baiia de Boch, 

 below the Chapel of Sant Medir near Llora. 



An area of rough lava, known as La Malatosquera or the 

 Bosch de Tosca, extends westwardly from the Fuente de San 

 Roque near Olot some two kilometers, the breadth being about 

 half the width. It is a wilderness of the roughest aa lava, 

 cultivated in spots and cut up by a labyrinth of walls and 

 narrow paths. Scattered over its surface are many small knolls 

 and protrusions of lava blocks cemented by finer-grained and 

 scoriaceous material. These do not seem to be definite cones as 

 reported by Grelabert, but are rather due to small, local explo- 

 sions of steam, and the heaping up of solid blocks, such as are 

 frequently found in extensive rough lava flows. This area, 

 which overlies a more compact and massive lava flow visible at 

 the fountain of San Roque, is apparently later than most of 

 the main flows, but is not connected with any definite cone, 

 for, though very close to that of Montolivet. it is yet clearly 

 distinct from this, and is probably to be considered as intermedi- 

 ate between the two phases of activity. 



The Cinder Cones. — Protruding through, and scattered over 

 the surfaces of these lava flows, and consequently later than 

 they, and in some cases resting on Quaternary deposits, are 



