Reviews — JSfasmyth and Carpenter on the Moon. 275 



they were produced under precisely similar conditions. Indeed, 

 under the conditions which seem to have prevailed from the first in 

 the moon it is possible to imagine that our globe itself might have 

 appeared less dissimilar to its satellite in outward aspect than it is at 

 present, the agents of its external change being confined to those of 

 volcanic order. Nay, it is conceivable that its rate of cooling due 

 to the loss of heat by radiation into auter space would, in the ab- 

 sence of any external coating of sedimentary rocks, water, or air, 

 have been so infinitely quicker that it might have long &ince assumed 

 the inert and lifeless character of the moon itself — its internal heat 

 exhausted, a spent planet. From this terrible fate it seems that we 

 have been hitherto preserved by the continual play of opposing 

 forces, from within and from without,, secured to our earth by its 

 aqueous and aerial envelope. 



Assuming,, however, the surface matter of the moon to be more or 

 less of the nature of our plutonic and volcanic rocks, and to have 

 been consolidated from a condition of igneous fusion, which seems on 

 cosmical grounds to be reasonable, the question remains, what was 

 the character of the eruptive forces to which the peculiar features of 

 this surface are owing ? Were they identical with or even similar 

 to the volcanic action which has operated on the crust of our globe ? 

 and if any difference is to be suspected, in what does it consist, and 

 in what may we suppose it to have originated ?: An inspection of 

 the portions of the lunar surface so ably photographed in the work 

 before us supplies some help towards the elucidation of this problem. 



It is difficult, upon such inspection, to resist the impression that 

 the main features of the moon's face are due to the sudden, rapid, 

 and violent ebullition of a liquid surface, occasioning the repeated rise 

 •upon numerous points, from the heated interior, of volumes of im- 

 mensely elastic vapour (bubbles I would call them, after Hooke), the 

 explosion (or bursting) of which exercised a powerful dispersive force 

 upon the superficial liquid matter, propelling it outwardly on every 

 side, both in spattering jets, and in concentric waves — the matter 

 thus driven away from the vent consolidating rapidly into an an- 

 nular bank or rampart around it at a radial distance determined by 

 the violence of the explosions. 



The subsequent more tranquil emission of the liquid matter 

 beneath, through the vent-holes thus established (a common occur- 

 rence among terrestrial volcanos), as well as from cracks caused by 

 deeper internal intumescence, or by the hydrostatic pressure of the 

 gradually contracting shell, will account for the partial or complete 

 filling up of the craters with lava, followed by its frequent outflow 

 from their breached sides ; as likewise for the still later exudation of 

 more viscid matter both from the central vents and from fissures 

 producing heaped up mountainous excrescences, as well as the bright 

 streaks described above ; while the complete consolidation and conse- 

 quent shrinkage of the surface will have given rise to those rectilinear 

 empty cracks which seem to indicate the last phase of the process. 



A view to some extent similar to this is advocated by MM. Nasmyth 

 and Carpenter. They, however, endeavour to account for " the 



