252 Tidal Disturbances caused by Eruption at Java. 



Krakatoa than at the nearest Indian station — an inference to be drawn 

 from the fact that all the recorded intervals between the negative and 

 positive waves increase as the distances from the centre of disturbance 

 diminish — the difference between General Strachey and Major Baird 

 will practically disappear. When we consider the absolute inde- 

 pendence of the two methods of deduction which they have respec- 

 tively employed, the facts of the one being derived from the atmosphere, 

 while those of the other are derived from the ocean, the coincidence 

 between the two results appears very striking. 



The Admiralty chart of the Eastern Archipelago shows that 

 Krakatoa is situated at the focus of what may be regarded as a 

 parabolic figure formed by the configuration of the contiguous 

 portions of the coasts of Java and Sumatra ; the axis of the figure is 

 directed westwards towards the Indian Ocean, and nearly at the apex 

 there is an opening to the north-east formed by the Straits of Sunda. 

 Thus the waves generated by an eruption at Krakatoa would be 

 mostly propelled towards the Indian Ocean, both directly and, though 

 in a minor degree, by reflection from the coasts ; the rush of waters 

 towards the coasts would only have one outlet, namely, the Straits of 

 Sunda, through which, as is well known, a great wave passed, carry- 

 ing widespread destruction for some distance beyond, along the 

 contiguous coasts of Java and Sumatra. This wave may possibly 

 have impinged with great force on the south-west coast of the island 

 of Borneo, which is on the prolongation of a straight line drawn from 

 Krakatoa through the Straits of Sunda. But to the north-west, at 

 Singapore, no trace of tidal disturbance appears to have been met 

 with ; a self -registering tide-gauge is established there, and the dis- 

 tance from Krakatoa is less than one-third of that of the nearest 

 Indian station ; but the Master Attendant reports that the gauge 

 records "no difference whatever in the tide." This may be due to 

 the fact that the wave through the Straits of Sunda, when it bent 

 round to the north-west towards Singapore, had but a shallow sea to 

 advance over, and its course must have been greatly impeded by the 

 numerous islands and shoals and the narrow straits and passages 

 between them ; thus it may have well broken up and disappeared at 

 some distance short of Singapore. 



In an appendix to his report, Major Baird gives the respective 

 velocities with which the great primary positive wave travelled to 

 Galle, the Mauritius, the coast of Africa, and three of his own 

 stations. He necessarily assumes that the as yet unknown time at 

 which this wave issued from Krakatoa is to be fixed from the known 

 time of its advent at Batavia, by deducting two hours from the latter 

 in accordance with the velocity table in Airy's Tides and Waves 

 already referred to. He obtains for the maximum velocity 467 

 statute miles per hour, both for Port Louis, in the Mauritius, distant 



