. 
¥uly 8, 1886] 
NATURE 
233 
‘ 
‘our shadows on the mist, encircled with rainbows, over the black 
inferno, 
We erected a survey signal for determining the location and 
height of the summit, and also of an important land boundary 
‘in the crater, viz. the corner where the four lands of Keauhou, 
“Kahuku, Kapapala, and Kaohe meet, which is at the cone in 
the central crater. We then descended the mountain, carrying 
more weight than was agreeable, until we were met by our 
natives bringing up our mules, for which we had signalled by 
fires. On the way down a violent thunderstorm was raging 
below us, while we were above in clear air, On my next trip 
up this mountain I found a tree on the slope below completely 
rent to splinters, and parts of it thrown several rods, by the 
lightning of this storm. 
During the next month I ascended the mountain again, this 
time carrying an excellent engineer’s transit. As I had no guide, 
1 marked most of the way up bystrips of cloth fastened to rocks 
to find the way back ; and taught by our former experience, I 
“took adonkey-load of fuel, as well us a load of grass for making 
a spherical survey signal, which served me several nights as a 
bed. When about half-way up the mountain, one of our pack- 
donkeys broke into a lava cave, and slid downwards nearly out 
of sight. It was extricated with great difficulty by a direct up- 
ward lift with ropes. I then sent one of my men down the 
mountain with the donkeys, retaining the other man with me. 
The first night on the summit was uncomfortable enough for us, 
with a storm from the north. At midnight we observed with a 
peehted candle that the roof of the tent was a-sparkle with ici- 
cles, and on touching it found it frozen stiff as a bullock’s hide. 
In the morning we found a beautiful sheet of snow an inch thick 
ver the tent and over all the ghastly blackness of the rocks. 
Tvery morning of our stay upon the mountain we found the 
water frozen in our kettles, and hoar-frost on the rocks. 
In the clear frosty air I was able with my transit to take the 
bearings of a dozen survey signals on the slopes and summit of 
Tualalai. 
i The new spherical signal which T had erected was afterwards 
accurately determined by observations from more than twenty 
Stations on Mauna Kea, Hualalai, and in South Kkona, and thus 
a trigonometrical station was at last located on the very summit 
of Mauna Loa. 
On the second day I descended from the west brink of the 
crater down the track of a high avalanche of rocks upon the 
second plateau, and again from this plateau by the path of 
another ‘avalanche into the central crater, stepping cautiously 
down upon the black floor of the crater, lest it should break 
under our weight. We found this caution unnecessary, for much 
of the crater bottom proved to be the most solid kind of 
pahoehoe. 5 
Here we stood as on the congea'ed surface of a tossing sea 
that had dashed its fiery surf thirty feet up on the surrounding 
walls, We travelled directly south for the cone, the boundary 
“corner, which I was to locate, erecting two flags about 2500 
feet apart for the ends of our base-line. In some places, where 
there appeared to have been violent action, the lava broke under 
our feet, letting us down into caverns. In some large tracts the 
pahoehoe was coyered with pumice, indicating the violence of 
_ the former surging and tossing of the lava, for pumice and other 
ight lavas seem to be the froth and foam of the fiercest erup- 
tions. Just before reaching the cone we came to a deeper basin, 
twenty or more feet below the rest of the crater bottom and 
about 400 feet wide, covered with the most friable lava, swollen 
“upwards as though raised by air-bubbles, and this basin extended 
in a lava flow to the north-east along the side of the crater. 
_ Probably this was the place of the last eruption, and of most 
of the eruptions of this central crater. We found the cone to 
be composed of pumice and friable lava still hot and smoking, 
and very difficult to ascend, but we succeeded in climbing to its 
‘top, 140 feet high, and in setting up a flag there for the boundary 
orner. We then descended between the east and west peaks of 
is cone over huge rocks and deep chasms. 
_ From the fact that this cone is represented on Mr, J. M. 
Lydgate’s map of 1874, I conclude that it has been of long con- 
finuance, probably composed of the cinders of successive erup- 
tions, and that the deep basin to the windward of it, like 
Halemaumau in Kilauea, has continued many years, and is 
situated at the great central volcanic throat of the mountain, 
5 I then returned to the second plateau to the north, and thence 
clambered out to the east of Mokuaweoweo by the extremely 
interesting route of a former cataract of lava from the summit 
a 
into the crater, the swift downfall of which had turned its lava 
almost into pumice, and the black, shining spray of which lay 
spattered on the surrounding rocks. 
Further south I observed the course of two other cataracts, 
which had poured directly into the central crater. At the 
summit I found the deep fissure from which the outbreak had 
come that caused these cataracts, and ascertained that it had also 
poured an immense stream north upon the first plateau and 
thence south to the central crater. Crossing from this place to 
the north over the first plateau I suddenly came to a frightful 
circular crater in the bed of the plateau, apparently 600 feet 
deep and tooo feet wide, with a cone in its centre still smoking. 
We were obliged to hurry with exhausting speed over rough lava 
in order to reach our tent before night. 
The next day we took the transit to the stations in the crater, 
and the next we surveyed with it along the western brink to the 
extreme south end, where we looked down into the south crater, 
which is about 800 feet deep and 2500 feet wide. The length 
of the whole chasm, or “caldera,” I have ascertained to be 
about 19,000 feet, the greatest breadth 9000 feet, and the 
greatest depth 800 feet. The area is three and six-tenths square 
miles. A map of these craters has been sent to the Government 
Survey Office, 
On the south-west side, near the junction of the central crater 
with the south plateau, I found that there had been another 
eruption, from fissures that were still smoking, and that this 
eruption had poured an immense stream southward towards 
Kahuku, and had also poured cataracts into the south crater 
from all sides. 
I had everywhere observed that there had been great flows 
from the summit brink down the mountain, and had wondered 
at the thought of the vast chasm having filled up and overflowed 
its brim. 
This, however, turned out to be an incorrect view. The flows 
have not been from the lowest parts of the brim, but from some 
of the highest, which could not have been the case in an 
overflow. 
The walls of the craters are largely composed of loose, old, 
weather-beaten rocks, and large tracts of the plateau are com- 
posed of old pahoehoe that has not been overflowed for ages, 
which would not be the case if the craters filled and overflowed. 
These outbreaks from fissures around the rim indicate that the 
lava has rather poured into the crater than out of it ; and that it 
has poured from such fissures in vast streams down the mountain- 
side. What enormous quantities of lava may flow from such 
small fissures is illustrated by the flow of 1859. The question 
arises, How has the lava risen high enough to pour in extensive 
eruptions through these fissures, almost a thousand feet above 
the bottom of the crater, without rising in the crater and over- 
flowing it? The same question has often been asked in respect 
to the rise of liquid lava to the summit of Mauna Loa without 
overflowing the open crater of Kilauea, 10,000 feet below. 
We have seen that it is not because the lava in Mokuaweoweo 
is lighter than that in Kilauea that it rises so much higher, In 
fact, it is as solid there as in Kilauea. ‘The explanation has 
occurred to me that molten lavas rise the higher the smaller the 
conduits in which they rise from their subterranean reservoirs. 
An illustration is afforded by the ‘spouting horns” on the 
sea-coast, where the ocean, rushing into caverns of rock, drives 
columns of water through small openings to the height of forty or 
fifty feet above high-water mark. We see another illust ration in 
water conveyed in pipes, which jets the higher the smaller the 
orifice. 
However violent the subterranean pressure may be, Kilauea 
does not overflow, but only rages the more fiercely, because its 
passage from the chambers below is so large. But through the 
yast mountain of Mauna Loa there is no doubt a constricted con- 
duit leading upward ; and there must be still smaller conduits to 
the fissures on the summit rim, On this theory, the molten lava 
rises higher through Mauna Loa than in Kilauea, because Mauna 
Loa has the smaller throat. 
It is therefore by no means certain that there is no subter- 
ranean connection between the two volcanoes. 
Another vexed question, of which several solutions have been 
proposed, is the mode of formation of the two strongly contrasted 
forms of lava known as “‘pahoehoe” and ‘‘aa.” The former 
term is applied to tracts of comparatively smooth and uniform 
lava, as though it had cooled while flowing quietly ; the latter to 
tracts of broken lava, as though it had cooled when tossing like 
an ocean in a storm, and had then been broken up by earth- 
