Reviews — Nasmyih and Carpenter on the Moon. 277 



one or more gaps, which gave issue to a stream of lava that flooded 

 the neighbouring surfaces. There are crater-lalces of this character 

 from 10 to 20 miles in diameter, and each attests the violent out- 

 burst of volumes of elastic vapour of enormous amplitude, and a 

 dispersive force equal to scattering to vast distances the materials 

 through which they explode in showers of fragments of lava, scoriae, 

 and the subjacent rocks, together with mud, sand, or ash mixed with 

 water, when, as seems to have been often the case, the eruption took 

 place beneath a shallow sea or lake. In this last case powerful con- 

 centric waves of semi-liquid matter will have been often propelled by 

 each explosion from the centre to the circumference of the basin, 

 where, mixing with the aerial fragmentary showers, they would 

 assist in forming the annular rampart. Now if we suppose ex- 

 plosive eruptions of this character to have burst through the serji- 

 liquid and probably molten and incandescent surface of the moon, 

 we have a process capable, I think, of explaining the appearances 

 presented by the lunar craters, not even excepting those of the 

 stupendous areas noticed above as usually called seas. 



These vast rings may have been the first effect of the erup- 

 tive action on the surface of the moon immediately after its con- 

 densation from nebular into liquid matter. It can scarcely be 

 inconceivable that disturbances of that surface may have then oc- 

 curred on a scale equal to the effect here indicated, when we look 

 to the eruptive phenomena still taking place on the solar disc, of a 

 character not altogether dissimilar, though infinitely more violent, 

 and affecting far larger areas. Even now, on our own planet, 

 oceanic Avaves, probably occasioned by submarine volcanic erup- 

 tions, have at times simultaneously invaded with great violence both 

 the east and west shores of the Pacific, affecting therefore an area 

 equal in diameter to a third of the circumference of the globe. 



The process to which I am here attributing the lunar craters may 

 perhaps appear extravagant in respect to the largest of them. But 

 it is difficult to draw a line of separation anywhere between large 

 and small. Nor, I think, ought the element of size to cai'ry much 

 weight in the consideration of the question. It is impossible to 

 assign a limit to the explosive force of expanding vapour or gases 

 at intense temperatures. Incandescent lava drops have been seen, 

 in some eruptions of Iceland, to be thrown up to vertical heights of 

 20,000 feet and more. The explosions of Tomboro in Sumbawa, and 

 of Coseguina in Central America, have, in recent eruptions, scattered 

 over thousands of square miles around their craters an amount of frag- 

 mentary matter sufficient, in either case, to build up an Etna. If we 

 admit that a succession of concentric waves may have propelled the 

 scoriae congealing on the surface of a boiling sea of lava to unite 

 with those falling after direct ejection from the vent in the formation 

 of an annular rampart around it, we might anticipate the instantaneous 

 solidification of the splashed-up lava there, owing to the absence of any 

 atmosphere to impede the dissipation of its heat into space ; and the 

 result might exhibit those precipitous and terraced interior cliffs and 

 the more gradual exterior slopes which the larger lunar rings so 



