168 
providing means by which large volumes of sea water might 
find access to the depths of the earth, through cracks and 
fissures which would naturally result. Dr Hector, of the New 
Zealand Geological Survey, in his preliminary report on the 
eruption of Terawera, says :— 
‘“*T have been informed that at the whaling settlement of Tawaite on the 
east entrance of Tory Channel, from six p.m. up to about eight p.m., on the 
evening of the 9th, loud booming reports were heard through the earth. As 
these reports were previous to any symptoms of the disturbance at Terawera, 
this suggests that they may have resulted from a slight movement along the 
great fault-line that traverses the north and south Islands in a north-easterly 
direction ; and, in this case, the immediate cause of the Terawera outburst 
may be found in a local fracture resulting from such movement.” * 
I must now say something with regard to earthquakes. An 
earthquake shock is transmitted through the strata of the earth 
in a series of waves which radiate from the centre of disturb- 
ance. The waves may be, to some extent, compared to those 
set in motion by a stone thrown into water, but there is this 
difference. In the latter case the disturbance is propagated 
outward by the action of gravity; in the case of earthquake 
waves they are the result of the elasticity of the rocks of 
the earth. It has been shown by Professor Milne (well 
known for his observations on earthquakes in Japan), that 
artificial earthquakes can be produced by exploding dynamite 
in holes in the earth. That being so we may conclude that 
if explosions occur in the interior of the earth earthquake 
shocks would result. I think it reasonable to assume, that 
if water, in large volumes, found access to the depths of 
fusion that explosions would follow; and we thus arrive at 
one possible cause of earthquakes. Professor Milne supports 
that theory as the cause of the greater number. He says:— 
“The majority of earthquakes are due to explosive efforts 
at volcanic force. The greater number of these explosions 
take place beneath the sea, and are probably due to the 
admission of water through fissures to the heated rocks 
beneath.+ It is, however, probable that some earthquakes are 
= “Nature,” vol. 34, p. 393. + Earthquakes, pp. 295-6. 
Miwa 
9 APR 1888 
>* es ats «3c uw. 
