Phillips. — 0)i the Volcanoes of the Pacific. 189 



Island in a general north-west and south-east direction, in- 

 cluding as far north as the Philippines, and so as to embrace 

 the greatest number of the Pacific islands. The actual trend 

 of the islands will be found lying generally in a west-north- 

 west and east-south-east direction, although many vary from 

 those points. 



Professor Milne places this area in his map as one of sub- 

 sidence, wherein it will be seen how greatly we differ. The 

 trinolith at Tongatabu happens to be a very good landmark as 

 to sea-levels, and it shows that that island, at any rate, has 

 not subsided 6 in. a century for the past three or four thousand 

 years. Instances are within our own knowledge of the rapid 

 growth of volcanic islands. " In 1796 a volume of smoke was 

 seen to rise from the Pacific Ocean about thirty miles to the 

 north of Unalaska. The ejected materials having raised the 

 crater above the level of the water, the usual volcanic phe- 

 Bomena occurred. Repeated eruptions have increased the 

 dimensions of the island until now it is several thousand feet 

 in height and between two and three miles in circumference." 

 So that there is really no geological objection to the upheaval 

 and formation of any of the groups of islands in the Pacific. 



I am at once met with the objection that there is no line 

 of present volcanic activity along the 20th parallel of south 

 latitude. That is so ; but nevertheless a glance at the map 

 shows that there has been a line of upheaval, and my duty is 

 to record in such a paper as this all the evidence I can collect 

 bearing upon volcanic action in the Pacific, a region which 

 hitherto has not met from vulcanologists that attention which 

 it merits — the grandest volcanic region, I take it, upon the 

 face of the globe. Great earth-oscillations doubtless occur 

 in this immense water-area — seventy million square miles. 

 There could not, of course, be so much volcanic activity with- 

 out this vast water-area. The pressure of 30,920 ft. of sea- 

 water near Tonga upon each foot of the ocean-bed at 62^ lb. 

 to the foot can be readily calculated. Such a column of water 

 would readily find out any weak crack or crevice to reach the 

 central heat or the imprisoned lava within the earth's crust. 

 But, of course, the more surface-water that pours in the more 

 quickly steam is generated, which by upheaval closes up the 

 fault or crevice. 



Thus, as I have already said, the bottom of the ocean is 

 blistered by upheavals and volcanic growths — viz., the various 

 groups of islands — and although we find no active volcanoes 

 along this third line, yet I am not prepared to admit that 

 volcanic action is quiescent, for one of the greatest tidal waves 

 on record within the past twenty-five years arose from a 

 submarine explosion in 21° 22' S. latitude and 71° 5' W. longi- 

 tude — the 1877 wave described by Milne and others, which, 



