1884.] on KraJcatoa. 87 



Francisco and Alaska, these disturbancies of the ocean were felt and 

 recorded. 



Still more striking were the vibrations propagated through the 

 more mobile material of the atmosphere. The effects produced on 

 the atmosphere in the vicinity of Krakatoa by the violently up-rushing 

 columns of vapour, and by its condensation, were indicated by frequent 

 and sudden changes in the height of the barometric column, and by a 

 terrible storm, of a strictly local character, which raged during the 

 whole time of the eruption. The investigations of Mr. Scott and 

 General Strachey have demonstrated that these disturbances were pro- 

 pagated in a series of waves, which, travelling at the rate of 700 miles 

 per hour, passed three-and-a-half times round the globe, recording 

 themselves on the barographs of meteorological stations all over the 

 world. 



The vibrations producing sound, whether carried by the land, the 

 ocean, or the air, made themselves felt over a circle with a radius of 

 2000 miles. 



The electrical disturbances, resulting in vivid lightning " fire- 

 balls," corposants, and a phosphorescent condition of the ejected 

 materials, were of the most startling character. 



The careful surveys undertaken since the eruption by the officers 

 of the Dutch Government, have shown that the whole of the island of 

 Krakatoa, except the high ridge on its southern side, was blown away 

 during the eruption, but that two adjoining smaller islands were 

 increased in size. To the north and north-east of Krakatoa, at a 

 distance of 7 miles from the centre of activity, two new islands 

 were formed where the sea had before a depth of about 20 fathoms. 

 As these new islands are entirely composed of loose fragmentary 

 materials, it has been thought that they were formed by the accumu- 

 lation of the ejecta from the central vent. There are strong grounds 

 however for the belief that lateral eruptions causing submarine 

 volcanoes accompanied the outburst from the central crater of 

 Krakatoa. The quantity of pumice thrown out during the eruption 

 was so great as to impede the navigation of the strait, and to cover 

 the ocean for thousands of square miles. 



Comparing the outburst of Krakatoa with that of Tomboro in 1815 

 we find that the quantity of material ejected in the latter was 

 according to Verbeek, from eight to eleven times as great as in that 

 of the former, while the area of darkness produced by the dust was 

 no less than nine times as great. On the other hand, it must be 

 remembered that the duration of the Tomboro eruption was more 

 than thirty days, while that of the Krakatoa was less than that 

 number of hours. Hence we are led to conclude that the Krakatoa 

 eruption, though of short duration, was of exceptional violence a 

 conclusion borne out by the fact that it was heard at distances twice 

 as great as the outburst of Tomboro. 



Of the interesting atmospheric effects, and especially the beautiful 

 sunsets, following the Krakatoa eruption, which have with a great 



