THE ORIGIN OF LUNAR VOLCANOES. 55 



There is one peculiar feature presented by the cones of 

 the cooling cinder which is especially interesting. The 

 flow of fused cinder from the little crater is at first copious 

 and continuous; then it diminishes and becomes alternat- 

 ing, by a rising and falling of the fused mass within the 

 cone. Ultimately the flow ceases, and then the inner 

 liquid sinks, more or less, below the level of the orifice. In 

 some cases, where much gas is evolved, this sinking is so 

 considerable as to leave the cone as a mere hollow shell; 

 the inner liquid having settled down and solidified with a 

 flat or slightly rounded surface, at about the level of the 

 base of the cone, or even lower. These hollow cones were 

 remarkably displayed in some of the cinder of the Hender- 

 son iron, and their formation was obviously promoted by 

 the abundant evolution of gas. 



If such hollow cones were formed by the cooling of a 

 mass like that of the Moon, they would ultimately and 

 gradually subside by their own weight. But how would 

 they yield? Obviously by a gradual hinge-like bending at 

 the base towards the axis of the cone. This would occur 

 with or without fracture, according to the degree of visco- 

 sity of the crust, and the amount of inclination. But the 

 sides of the hollow-cone shell, in falling towards the axis, 

 would be crushing into smaller circumferences. What 

 would result from this? I think it must be the formation 

 of fissures, extending, for the most part, radially from the 

 crater towards the base, and a crumpling up of the shell of 

 the cone by foldings in the same direction. Am I ventur- 

 ing too far in suggesting that in this manner may have 

 been formed the mysterious rays and rills that extend so 

 Abundantly from several of the lunar craters? 



The upturned edges or walls of the broken crust, and 

 the chasms necessarily gaping between them, 'appear to 

 satisfy the peculiar phenomena of reflection which these 

 rays present. These edges of the fractured crust would 

 lean towards each other, and form angular chasms; while 

 the foldings of the crust itself would form long concave 

 troughs, extending radially from the crater. 



These, when illuminated by rays falling upon them in 

 the direction of the line of vision]! must reflect more light 



