130 Captain Roz^t (m the Surface of the Moon. 



the great greyish spaces, which is also that of the rings ; and 

 a scoriaceous crust, elevated above that bottom to a height 

 which has been measured at a great number of points. These 

 measurements have afforded me the means of calculating the 

 thickness of this crust, and. I found that the mean is 642 

 metres (2106 English feet). 



From all the facts I have ascertained, and from all the de- 

 ductions to which these facts have led me, I think I may draw 

 the following conclusions :— 



1. The lunar globe has originally been in a state of fusion, 

 and has been gradually cooled. 



2. During the formation of the external scoriaceous pellicle, 

 there existed in the mass whirlpools or circular movements, 

 which, driving the scoriae from the centre to the circumfer- 

 ence, formed annular ridges, by the accumulation of those 

 scoriae at the limit of the undulation. When several whirl- 

 pools occurred in such circumstances, that the distance of the 

 centres, taken two and two, was less than the sum of the 

 radii, there resulted an enclosed space, bounded by arcs of 

 circles. When the distance of two centres was greater than 

 the sum of the radii, two complete rings were formed. 



3. The amplitude of the whirlpools diminished with the 

 fluidity of tlie surface, but the phenomenon continued through- 

 Out the whole duration of the process of consolidation. 



4. The mode of formation which we assign to the lunar 

 rings, altogether excludes the idea of craters resembling those 

 of our volcanoes. 



5. The surface of our satellite being thus consolidated, no 

 solid or liquid layer coming from the exterior was subse- 

 quently deposited upon it ; for, otherwise, the small rings and 

 the fissures would have disappeared. The perfect preserva- 

 tion of all these variations in external configuration, shews 

 that no liquid has ever existed in considerable quantity, 

 either at the surface, or even in the atmosphere of the moon. 



6. After the complete consolidation of the external enve- 

 lope, the matter which remained fluid in the interior acted 

 upon that envelope, and fractured it, often giving rise to large 

 radiating cracks. At that epoch, the solid crust must have al- 



