SUMATRA 
169 
it, but to the south-east the tide gauges of West Australia 
showed marked evidences of its having reached those 
shores. 
Still more extraordinary were the air waves produced 
by the violent explosions. Here, again, we find, as in the 
ease of the sea waves, that there was one pre-eminent in 
strength and volume. It appears very nearly to have 
coincided with the gigantic seismic wave just discussed, 
and the character of the disturbance would seem almost 
incredible, were it not for the fact that it is attested by 
the barograms of every great meteorological station on the 
world’s surface. Shortly, it was this: that the circular 
wave or oscillation having Krakatau as its centre pro¬ 
pagated itself over the entire surface of the globe until it 
reached the antipodes of the volcano ; that it was thence 
reflected back or reproduced, travelling backwards to its 
point of origin, from which it again returned; and that 
in this manner the occurrence of the wave was observed 
no fewer than seven times—four passages having been 
those of the wave travelling from Krakatau, and three 
those of the wave travelling from its antipodes. From 
this the time of its genesis could easily be calculated with 
tolerable exactitude. It is given by Lieutenant-General 
Strachey as 2 hours 56 minutes Greenwich mean time, 
which in local time would correspond with 9.58 o’clock 
on the morning of the 27th August. 
The distance at which the sounds of the eruption were 
audible is much in excess of anything previously recorded ; 
indeed, one of the reports is of special interest, as being 
the only instance known of sounds being heard at any¬ 
thing like so great a distance from their place of origin. 
The island of Kodriguez in the Indian Ocean is about 
2968 miles from Krakatau in a direct line, yet the noise 
of the explosions was heard during the night of the 26th- 
