The principal charm of astronomy, as indeed of all observational science, lies in the study of change--of progress, development, and decay, and specially of systematic variations taking place in regularly-recurring cycles.

And it is in this relation that the moon has been so disappointing an object of astronomical observation.

For two centuries and a half her face has been scanned with the closest possible scrutiny; her features have been portrayed in elaborate maps; many an astronomer has given a large portion of his life to the work of examining craters, plains, mountains, and valleys, for the signs of change; but until lately no certain evidence--or rather, no evidence save of the most doubtful character--has been afforded that the moon is other than "a dead and useless waste of extinct volcanoes." Whether the examination of the remarkable spot called Linne--where lately signs were supposed to have been seen of a process of volcanic eruption--will prove an exception to this rule, remains to be seen.

The evidence seems to me strongly to favour the supposition of a change of some sort having taken place in this neighbourhood.
The sort of scrutiny required for the discovery of changes, or for the determination of their extent, is far too close and laborious to be attractive to the general observer.

Yet the kind of observation which avails best for the purpose is perhaps also the most interesting which he can apply to the lunar details.