Miscellaneous Papers. 



261 



Photograph of semi-fluid plaster on which pebbles were thrown just prior 



to its setting. 



as some of the yet remaining fragments are still coming to 

 us in meteors and meteorites. 



Now, everyone has noticed that a pebble dropped into a 

 pool of water will produce a series of concentric waves, and, 

 as the displaced water returns over the pebble, a little cone 

 is raised, which subsides again, as do also the waves. Now, if 

 this experiment be tried in a semiliquid, the first wave will 

 go but a short distance and retain its wave shape, and the 

 central cone will rise but not subside as in water, and the less 

 fluid the substance, the more marked will be the result. 



This, I claim, is just what happened on the moon. As it 

 began to cool, the belated fragments came plunging into it 



