170 PICKERING. — LUNAR AND HAWAIIAN PHYSICAL FEATURES COMPARED. 
Figure 23 represents a spiracle fourteen feet in height by six feet in diameter at 
its base, found in Kilauea near Halemaumau. It is built up of what may be described 
as great drops of solidified lava. The interior tube is open at the top and measures 
a foot in diameter. Another somewhat smaller spiracle is seen in the background. 
Often several spiracles occur side by side with confluent bases, as in Figure 24. This 
object is also located in Kilauea, near the corral where the horses are left. It closely 
resembles the central peak or range of peaks so often found in the lunar craters, and 
is doubtless due to the same cause. See Tycho and Longomontanus, Figure 16. It 
is ten feet in height. Several of the spiracles forming it are open, and several are 
closed. There are a number of large cavities in the interior, in some of which were 
found some very slender lava stalactites. No lava flow had escaped from any of the 
craters, but two outbursts had occurred upon the side, and may be seen about half 
way down the slope, below the right-hand summit of the ridge. 
Figure 25 shows a much larger row of spiracles found on Hualalai. They measure 
about a thousand feet in height above their base. Midway between the two highest 
summits are two smaller ones. The left hand of these is known as the Bottomless 
Pit. The little cone measures one hundred feet in diameter at its base by sixty feet 
in height. A narrow tube a few yards in diameter opens at the summit, and it is 
said that it has been sounded for 1400 feet without reaching bottom. Whether 
this figure is correct or not, doubtless the tube is very deep, and no bottom is 
visible. These spiracles equal in height many of the central peaks found upon the 
Moon. 
Sometimes a row of small conical elevations, about equally spaced, occurs upon 
the Moon. Such a row is found in the eastern part of the floor of Wilhelm I, the large 
crater shown in the lower right-hand corner of Figure 16. The illustration is on too 
small a scale to show them to advantage, however. A row of still larger cones is found 
just outside and northeast of the crater. They seem like spiracles thrown up along 
the course of a steam crack. 
Sometimes the lava slabs pile up on one another in horizontal layers, as in 
Figure 26, and sometimes much more irregular blocks occur, without any apparent 
order. These form pinnacles with very steep sides and ends. Their origin seems to 
be due to recent flows of lava which have transported and piled up the fragments 
formed from the earlier flows, somewhat as the ice pack is transported by the winds 
and currents in the far north. This object was found in Kilauea. 
Another type of pinnacle consists of a single block of lava which may rise as high 
as sixty feet above the surrounding plain. The sides are often precipitous, and there 
