160 PICKERING. — LUNAR AND HAWAIIAN PHYSICAL FEATURES COMPARED. 
At times the surface solidifies, then suddenly a crack will run across it, and in a 
hanging. A. J. S., XCVII, 96. In A. J. S., CXVIII, 227, it is stated that the 
depth was 400 feet and that the distance across the bottom was one mile less one 
hundred feet. It is also stated that the pit had formerly been filled up not only from 
the bottom, but by lateral discharges from the walls. 
A year later Halemaumau had filled to within 100 feet of the top, the level area 
with „ 
glit small apertures within which the liquid lava could be 
boiling fiercely 50 to 100 feet below the surface. A few months later the lava was 
within 2o feet of the rim, and the diameter of the pit was said to have enlarged to 
over a mile. A. J. S., XCIX, 393. 
In 1870 the pit overflowed, the lava pouring down and partly filling the north- 
eastern depression. At the time of an eruption such as this, the lava rises, overflows 
and cools thus forming a raised rim or circular dam. Such a rim is shown on a 
small sea e m the slag crater, Figure 11, and on a much larger scale in the photo- 
graphs of Halemaumau, Figures 12 and 13, the cakes of lava there represented 
appearing much like broken cakes of ice. In Figure 14 is shown a portion of the 
Moon near the hmb, so as to present the craters obliquely. It will be noted that the 
few minutes the whole solid material will break up into separate cakes which will 
presently turn on edge and sink beneath the surface of the lake. This again solidifies, 
and in a few hours the process is repeated. See report of the United States Geo- 
logical Survey for 1883, p. 106, Major C. E. Dutton. 
These lakes are especially interesting to the selenographer, since about them are 
formed crater rings, which seem to be analogous in appearance to the larger crater 
formations upon the Moon. During the past forty years, since the construction of the 
hotel upon the rim of Kilauea, they have been very carefully observed, and it will 
therefore be well in this place to deal with the subject, briefly, from the chronological 
standpoint. All the earlier descriptions which follow are condensed from the writings 
of the Rev. Titus Coan. The references given refer to the American Journal of 
Science. 
On April 2, 1868, a severe earthquake shook the southern coast of Hawaii, and 
for the next five days a subterranean discharge of lava took place from Kilauea. As 
a result of this discharge the central area to the northeast of Halemaumau sank about 
300 feet, carrying with it the vegetation still growing on its surface. The walls of 
this new pit were inclined from 30° to 60°. The lava also flowed out of Halemaumau, 
leaving a circular pit 3000 feet in diameter at the top, 1500 feet at the bottom, and 
500 feet deep. Its walls were in some places vertical, and in some slightly over- 
