38 VOLCANOES 



The first recorded eruption of Vesuvius is that which occurred 

 in 79 a.d. and is described in two letters written to Tacitus by the 

 younger Pliny. In this frightful paroxysm little or no molten lava 

 was ejected, but the old cone was partly blown away (its remnant 

 now forms the outer ring, called Monte Somma), and so enormous 

 was the quantity of ashes that at Misenum, across the bay of 

 Naples, the sun was darkened, as Pliny reports, " not as on a 

 moonless cloudy night, but as when the light is extinguished in a 

 closed room ... In order not to be covered by the falling ashes 

 and crushed by their weight, it was often necessary to rise and 

 shake them off." Herculaneum was overwhelmed with floods of 

 ashes mixed with water, while Pompeii was completely buried in 

 dry ashes and small fragments. 



This first historical eruption of Vesuvius was thus of the type 

 known as explosive, which is exhibited in its extreme form by 

 several of the East Indian volcanoes, and preeminently by Kra- 

 katoa, the eruption of which in 1883 was the most frightful ever 



FIG. 6. — Profiles of Krakatoa. The full line is the present condition, the dotted 

 line the condition before the eruption of 1883. (Judd.) 



recorded. This volcanic island, situated in the Strait of Sunda, 

 was little known, except that it had been in eruption in 1680. As 

 the island was uninhabited, the earliest stages of the outburst were 

 not observed, but on May 20 a great cloud of steam was seen over 

 the vent. The catastrophe occurred in August, when, besides the 

 fearful devastation caused by the disturbances of the sea on the 

 coasts of Sumatra and Java, the island itself was almost annihilated. 

 Hardly one-third of its original surface was left above water, and 

 where formerly was land are now depths of 100 to 150 fathoms of 

 water. The force of the explosion produced waves in the atmos- 

 phere which were propagated around the whole earth, and the 

 first one was observed in Berlin ten hours after the explosion. 



