174 PICKERING. — LUNAR AND HAWAIIAN PHYSICAL FEATURES COMPARED. 
A large crack is found in Kilauea in precisely this position, Figure 30. It is from 
6 to 8 feet wide and from 20 to 30 feet deep near the bridge. It is said to be 
about a mile in length. A crack 5 to 20 feet in breadth, and 40 to 200 in depth, 
by 16 miles in length is located southwest of the crater, and a similar one 
parallel to it is found near by. Several cinder cones occur upon these cracks much 
as crater pits do upon the Moon. The cracks themselves have been partly filled up, 
but one said to be 1500 feet in depth and 5 to 15 in width is situated not far from 
the Sixth Crater near Kilauea. 
Keanakakoi is a small crater one and a half miles southwest of Kilauea Iki. 
Its floor measures 500 feet in diameter and is 300 feet below the rim. It illustrates 
the craters having smooth floors upon the Moon. The lava surface itself is wonder- 
fully smooth, but a close inspection shows that it has a convex surface, rising from 
10 to 15 feet higher at the centre than at the edges. In this respect it also 
resembles what we find upon the Moon. The surface is slightly undulating, the 
hillocks measuring perhaps two feet in height above the depressions, thus indicating 
compression of the floor. The surface is also everywhere seamed with cracks, from 
one to three inches in breadth, and running in all directions. This indicates subse- 
quent contraction. As often occurs upon the Moon, a crack was found running 
parallel to the edge of the floor, and not far from the walls. Seven prominent radial 
cracks were counted. The arrangement strikingly resembled that of the rills in 
Gassendi. A good map of this crater is given in " The Moon," by Neison, p. 337. In 
no place did the cracks exceed eight inches in breadth. Ferns are beginning to 
grow in these here and there. 
A very different type of crack is sometimes produced where the surface is forced 
open by a subterranean lava flow, and small craters and blow holes are formed 
along its length. Such a one is found at Huehue, due to an eruption on the slopes 
of Hualalai in 1801, Figure 33. A ridge 50 feet in height in some places, and 
carrying on its summit a crack 30 feet wide by 40 feet deep, and extending for 
perhaps a mile has been produced. It is very irregular in outline. 
Such a crack is represented upon the Moon in Figure 32. It is a good illustration 
of the crater rills so called, and is known as Bullialdus <f>. The straight portion 
measures 40 miles in length by perhaps one and a half in breadth. Its edges are 
elevated as in its Hawaiian representative, and are quite as irregular in outline in 
proportion to its size. The distinction between these two types of rills is not sharply 
drawn upon the Moon, and the same rill sometimes exhibits both types in different 
portions of its length, as is the case with three small rills located on the northeastern 
