BY THE REV. J. E. TENISON-WOODS, F.G.S., &C. 703 



area of volcanic disturbance or the subterranean fires is veiy 

 lars;e, extending, as it does, for fifty or sixty miles in a straight 

 line, and in some places of almost equal width. Now in a volcanic 

 eruption many a fissure and many a fiery jet become covered up 

 and obliterated by the immense fall of ashes and cinders, but, of 

 course, only to break out in some new direction close by. The 

 one centi-al point is the volcano, but even this is full of little 

 craters inside it, as we shall see presently. One is disappointed at 

 seeing so little of the fires, but the}' are so completely covered 

 with ashes and scoria?, that sulphurous vapours and steam are the 

 only evidence that we see of what is going on underneath. Every 

 now and then a more powerful explosion casts the light and porous 

 covering of cinders into the air, but the most of this falls back 

 again and the vapour goes on escaping as before. What we see 

 at Las Canas is similar to Vvilcano in the Lipari Isles of the 

 Mediterranean, in which, by the shifting of the centre of volcanic 

 activity along a line of fissure, a series of overlapping volcanic 

 cones has been produced. 



It will be seen subsequently that there is reason for believing 

 that the whole of the lake around the volcano is an area of sub- 

 sidence, which represents the former extent of an immense volcanic 

 cone. We have, therefore, according to this theory, only a portion 

 of the later history of the volcano revealed to us, with the evidence 

 of those forces which have tended to modify the form and 

 character of this volcano, which, according to Mr. Judd's classi- 

 fication, is one of composite character. In his Work on Volcanoes 

 he points out (p. 161), that the sides of such cones are liable to be 

 rent asunder from time to time, and the fissures so produced are 

 injected with liquid lava from below. These fissures rent in the 

 sides of volcanic cones often reach the surface, and eruptive action 

 takes place, giving rise to the formation of a cone or series of 

 cones upon the line of fissure. Such small cones thrown up on the 

 flanks of a great volcanic mountain are known as parasitic, and, 

 though subordinate to the mountain mass, they ai'e sometimes 

 themselves of considerable dimensions. Amongst the hundreds 

 which stud the flanks of Mt. Etna, there are some nearly 800 ft. 

 high. 



