208 THE STORY-BOOK OF SCIENCE 



"No, not the people, for lava runs very slowly, on 

 account of its sticky nature, and one can be warned in 

 time ; it was the town itself that ran the greatest risk. 

 The quarters invaded by the lava were the highest ; 

 from there the current could spread everywhere. So 

 Catania seemed destined to total destruction, when 

 it was saved by the courage of some men who at- 

 tempted to battle with the volcano. They bethought 

 themselves to construct stone walls, which, placed 

 across the route of the on-coming stream, would 

 change its direction. This device partly succeeded, 

 but the following was the most efficacious. Lava 

 streams envelop themselves in a kind of solid sheath, 

 embank themselves in a canal formed of blocks co- 

 agulated and welded together. Under this covering 

 the melted matter preserves its fluidity and continues 

 its ravaging course. They thought, then, that by 

 breaking these natural dikes at a well-chosen spot, 

 they would open to the lava a new route across coun- 

 try and would thus turn it from the town. Followed 

 by a hundred alert and vigorous men, they attacked 

 the stream, not far from the volcano, with blows of 

 iron bars. The heat was so great that each worker 

 could strike only two or three blows in succession, 

 after which he withdrew to recover his breath. How- 

 ever, they managed to make a breach in the solid 

 sheath, when, as they had foreseen, the lava flowed 

 through this opening. Catania was saved, not with- 

 out great loss, for already the lava flood had con- 

 sumed, within the town walls, three hundred houses 

 and some palaces and churches. Outside of Catania, 

 this eruption, so sadly celebrated, covered from five 



