154 PICKERING. — LUNAR AND HAWAIIAN PHYSICAL FEATURES COMPARED. 
I 
most numerous group, and most widely distributed throughout the islands. They 
have no outer slopes whatever, consisting simply of a pit sunk in the ground. Their 
walls are sometimes vertical, descending without talus to a flat floor ; sometimes the 
talus is present, and may cover the whole floor, leaving the bottom as a conical pit. 
Sometimes the walls are inclined, descending at a uniform slope to a flat floor. The 
slope in this case is usually steep, — perhaps 45°. The crater rings are the rarest 
type, and resemble the larger craters found upon the Moon. They have flat floors 
and sloping inner and outer walls. The crater bowls differ from them in that the 
bottom instead of presenting a well-defined flattened floor is concave, the curvature 
being continuous with that of the walls. They are identical in appearance with 
most of the smaller lunar craters. Section drawings illustrating these different forms 
will be found on p. 171, and will be described when the various types are reached. 
Photographs of many of them are also given at the end of this memoir. 
In addition to the craters, there are found numerous other interesting formations, 
such as lava caves, channels, cracks, spiracles, pinnacles, ridges, etc. A spiracle is 
literally a blow hole, but in this paper, for lack of a better name, I have used the 
word to indicate the solid formation surrounding the hole. In dealing with these 
various objects it has been thought best to describe each class by itself, stating where 
the best specimens of each may be seen. 
The visitor to Hawaii, on entering the harbor of Honolulu, is at once struck with 
two very conspicuous volcanic formations, known as Diamond Head and the Punch- 
bowl. Other smaller and less conspicuous craters, of the same general type, will be 
found in the immediate vicinity. The Punchbowl, a, p. 171, reaches an altitude of 
498 feet, and is situated within the city limits. The crater is but slightly concave, 
being filled nearly to the brim, and has a diameter of 2500 feet. The writer did 
not have an opportunity to examine it carefully, but as it was evidently similar 
to Diamond Head, 6, p. 171, which was larger, and apparently better preserved, this 
was not greatly regretted. 
From every direction Diamond Head, Figure 1, presents an appearance similar to 
a unar crate, Its highest point reaches an altitnde of only 761 feet above the sea, 
th rim t? , the Crater rim meaSUreS 3200 ^ "00 feet. An ascent of 
tn ZZ V L^ fr ° m ' P ° int ° D the r0ad 3« st Wond the terminus of 
1 r oTr T 7 at this point has an altitude ° f 45 ° *•* In *• 
„ I ' ^ CTater '. S ° meW hat t0 one *><> of the centre, is located a shallow lake. 
dry, whose bed measures 220 feet hplnw ^ -• ' u 
, , v ieei De AOw the rim where we crossed 
It 
surrounded by a verv dense ^.a * .u W088eu Ifc 
y very dense growth of thorny shrubs. Within the crater was found 
