J. D. Dana— Volcanic Action. ila 
The first of the operations mentioned above is necessarily the 
same. 
The second method of work and its consequences must also 
be the same; for vapors rise and escape from the crater in great 
abundance during periods of special activity, as attested to by 
many observers. For years the outside waters needed to af- 
ford the working steam gain access quietly ; but at times there 
have been large incursions, as proved by the violence of the 
earthshakings, the vast amount and height of the cloud of 
vapors, and the lofty projection of cinders. 
The recent eruption in the Tarawera Geyser district, New 
Zealand, affords an example in which only fresh waters were 
concerned, and one of much instruction. The Tarawera 
mountain, its height about 3,600 feet above the sea level, though 
made of volcanic rocks, had, previous to the eruption, as Mr. S. 
Perey Smith reports from observations in 1874, no distinct 
erater. On the morning of the 10th of last June, after some 
rumblings for an hour, the mountain (at 2.15 A.M.) was rent 
from north to south; three craters were seen to be in action; 
and soon after, as later observations have shown, there were 
seven craters in the course of 23 miles along the top of the fis- 
sured mountain, and other small craters on what was properly 
an extension of the fissure six miles to the southwest. Black 
clouds, lighted below by the fires, rose to a height of ‘10,000 to 
12,000 feet,” and red hot scoria and cinders were shot up a thou- 
sand feet or more. The rain fell with the falling cinders in tor- 
rents, accompanied with the thunderings and shifting winds of a 
tornado. By daylight the village of Wairoa, five miles distant, 
was covered a foot deep with mud, made from the ejected cin- 
ders or volcanic ashes, and the descending waters (rain). 
Three days later, the action in the mountains had mostly 
dwindled to steaming fissures, and on going to the region, it 
was found that the fissure, which was over two hundred yards 
wide, passed through Lake Rotomahana, 1 X 4 m. in area; 
that the lake had lost its water; that the bottom was 250 feet 
below its former level, and in it there was a line of mud craters 
and geysers, one of the craters throwing the mud to a height of 
600 to 800 feet. Hvidence of the work of ejection and engulf- 
ment in the mountain existed in the great size of the fissure 
opened, and also in the depth and size of the mountain craters, 
one of them 900 feet deep, another 600, with five others of less 
depth, besides a great sunken area, 2000 feet long, 600 wide, 
and 250 to 800 deep in the southwestern slope of the Tarawera 
mountain facing Lake Rotomahana. There can be no doubt 
here that in this great outbreak, so sudden, so abundant in cin- 
der ejections (but no flow of lavas), the lost waters gained access 
to the fires under the mountain. he waters were in so great 
