236 THE ERUPTION OF KRAKATOA IN 1883 



Krakatoa, the barometers failing to record the fourth return of the 

 wave. 



The velocity of the wave varied from 674 to 726 English miles per 

 hour, being very nearly equal to the velocity of sound in air at 50 

 P'ahrenhcit, which is 757 miles. There is no direct evidence, however, 

 that the great explosion producing the wave was accompanied by 

 sounds sufficiently loud to be heard at any great distance. The time 

 occupied by the wave passing around the earth was about 36 hours. 

 The wave moving with the rotation of the earth traveled with a slightly 

 greater velocity than that going in the opposite direction, viz. about 

 28 English miles per hour. This difference is supposed to be due to 

 the winds that blow in a general westerly direction on the path followed 

 by the wave. From the velocity of the wave it has been attempted to 

 deduce the time of the great explosion, and the result agrees very closely 

 with the record made by the gasometer at Batavia; for, when the wave 

 passed over that place, the gasometer leaped from its well, and left a 

 plain, though not very delicate, mark of the time. As thus determined 

 the explosion occurred at 9 hours 58 minutes, local time, on August 

 27. 



Sea Waves 



No sea waves were caused by the eruption of Krakatoa during 

 May, but on the morning of August 27 several small ones inun- 

 dated the shores of Sumatra and Java, partially destroying the towns 

 and villages, and causing the death of many of the inhabitants. The 

 number and size of the waves that followed are not known, for the 

 people had fled terror-stricken to the hills, and, surrounded by 

 darkness, were but little fitted to note the changes about them. The 

 most destructive waves followed the great explosions of the volcano 

 some time after ten o'clock on the morning of August 27. From the 

 data collected by Mr. Verbeek it has been calculated that the largest 

 of the waves was about 50 feet high before it reached the shore, 

 although the traces it left on the land show that it rose 70 feet above the 

 sea level, and its height has been estimated by some as great as 125 

 feet. The smaller waves are supposed to have been due to the sudden 

 evolution of steam, caused by the contact of the sea and the molten 

 lava, and by the fall of huge portions of the volcano. The origin of 

 the great wave is an unsettled question. It has been assumed that 



