330 



F. A. Ferret — The Flashing Arcs 



produced them, but the place of observation was probably too 

 near the crater. The small eruption of Etna in 1908 was not 

 observed, but the conditions were not, in my opinion, such as 

 to have reproduced the phenomenon. At Teneriffe in 1909, 

 although incandescent lava was still available for research work 

 upon my arrival, the explosive effects, which had been pow- 

 erful, were virtually at an end, and it was therefore with the 

 greatest delight that during the 1910 eruption of Etna I again 

 observed the flashing arcs. 



Fig. 1. 



By a rare good fortune the explosions in this case were 

 almost without detritus, thus forming a condition the very 

 opposite to that at Vesuvius in 1906. It will be remembered 

 that this eruption of Etna produced a fissure 2 km in length over 

 which were formed some twenty-four small craters. The 

 explosive forces were thus so subdivided and distributed that 

 no very large cones of scoriae were built up, many of the cra- 

 ters being little more than holes in the ground. One of these, 



