1864.| Nasmyri on the Physical Aspects of the Moon’s Surface. 397 
immediately precedes or accompanies solidification. It is, therefore, 
in this expansion in the bulk of the solidifying matter, beneath the 
Moon’s crust, that we are to look for the true cause of that eruptive 
or ejective action which has resulted in the displacement, swrface- 
ward, of the fluid portion of the Moon’s internal substance ; a dis- 
placement which has manifested itself in nearly every variety of 
voleanie formation, such as circular craters with their central cones 
or mountains of exudation, cracked districts, &c.; all these varia- 
tions of well-recognized volcanic phenomena being intermingled 
and overlaid one upon the other in the most striking and wonderful 
manner. In illustration of this, I would here refer the reader to 
the lithograph which accompanies this paper, and which has been 
selected as a fair type of the greater part of the lunar surface where 
such volcanic features are characteristically displayed. 
It may, however, be very reasonably and naturally asked, “ What 
evidence have I that the features I refer to have any relation to 
voleanic action at all?” In reply to such a question I would direct 
the inquirer’s attention to one single feature which, I conceive, 
demonstrates more completely than any other the fact of volcanic 
action having (at however remote a period) existed in full activity in 
the Moon. ‘The special feature to which I would refer is the central 
cone that may be observed within those “ Ring-formed mountains,” as 
they have been termed. “The central cone” is a well-known and 
distinctive feature in terrestrial volcanoes. It is the residue of the last 
expiring eftorts of a once energetic eruptive volcanic action, which 
had thrown the ejected matter to such a considerable distance round 
about the volcanic vent, that in its descent it had accumulated around 
in the form of a ring-shaped mountain or crater, whilst on the subsidence 
of this volcanic energy, the ejected matter was deposited in the 
immediate vicinity of the vent or volcanic orifice, and thus arose the 
* central cone.” 
Anyone who is familiar with terrestrial volcanic craters must, at 
the first glance at those which are scattered in such infinite numbers 
over the Moon’s surface, detect this well-known analogous feature, 
the central cone, and at once reasonably infer that these similar forms 
arose from a common cause, that cause being no other than volcanic 
action, accompanied by all its most marked characteristics. 
Fie. 1. 
Fig. 1. Represents a fair average type of the structure of a 
Lunar Volcanic Crater with its central cone A. 
252 
