618 
POPULAK SCIENCE REVIEW. 
pigmy caves — small at least in comparison with the other 
circular formations — have a small peak at the centre. That 
they are volcanoes can scarcely be doubted^ and perhaps the 
expiring efforts of the volcanic force,, as all the older forma- 
tions are thickly covered with them. The mountain- chains 
are those which show the least approach to volcanoes, and 
bear the greatest resemblance to the great chains on the 
earth ; and were it not for the appearance of a crater occa- 
sionally, they might be considered as belonging to the same 
terrestrial groups after which they are named; viz., the Alps, 
the Apennines, or Carpathian hiUs. They are mostly situated 
in the northern part of the moon, and are very white and 
bright. So high and extensive are the Apennines that this 
chain can be seen with the naked eye, when the moon is 
about half-full, and when it appears to be bulging into the 
dark space. The chain of the Alps is remarkable for a deep 
pass, which almost cuts it in two, and bristles with peaks 
and mountains. 
Among the latest formations on the moon, Maedler reckons 
the long straight lines appearing when the moon is full, like 
pieces of thin white thread stretched over its surface, but at 
• the other phases seeming quite black. There can be no doubt 
but that they are fissures, and it has been noticed that they 
occasionally pass through a succession of craters, as if some 
force acting underneath had split open the ground between 
the latter. They are between ten and a hundred and fifty 
miles long, and not more than five thousand feet broad ; but 
their depth is unknown, although the writer would judge, 
from the appearance which one presented, when viewed under 
favourable cmcumstances, at the broken edge of the moon, 
that it was fully equal to its breadth. They are best seen in 
the seas,’"’ but are also to be met with in the interior of the 
circular mountains, and it sometimes happens that the fissm^e 
passes through the walls. They are generally quite straight, 
but a few may be seen which are more or less curved, and their 
edges are slightly raised. They are most favom*abiy observed 
in the Sinus Medii, in the neighbourhood of the mountains 
Hyginus and Triesnecher, where they appear like the branches 
of a river, which, indeed, some have conjectured them to be, 
although now divested of water.* Far more extensive and 
distinct than those are the vast and bright radiating streams, 
* The terrestrial phenomena of the dykes of Monte Somma, in Vesuvius, 
may be of the same nature, in the same manner as one of the mountains 
near Clermont may be compared to the annular mountains, or the group 
round the great volcano of J omllo, as given by Humboldt to the surface of 
the southern hemisphere of the moon. 
