THE FRIENDLY ROCKS 



third of a mile away, I uncovered other rock sur- 

 faces on the same level, that showed a continuation 

 of the same lines. The great jack-plane had been 

 shoved across the valley and over the mountain- 

 tops and had taken off rocky shavings of unknown 

 thickness. 



The drift boulders are not found beyond the 

 southern limit of the great ice-sheet — an irregular 

 line starting a little south of New York and running 

 westward to the Rocky Mountains, but in southern 

 California I saw huge granite boulders that looked 

 singularly like New England drift boulders. They 

 cover the hill called Rubidoux at Riverside. I over- 

 heard a tourist explaining to his companions how 

 the old glaciers had brought them there, apparently 

 ignorant of the fact that they were far beyond the 

 southern limit of the old ice-sheet. It is quite evi- 

 dent that they were harder masses that had weath- 

 ered out of the place rock and had slowly tumbled 

 about and crept down the hill under the expansive 

 power of the sun's rays. But I saw one drift boulder 

 in southern California that was a puzzle; it was a 

 water-worn mass of metamorphic rock, nearly as 

 high as my head, at the end of a vaUey, several 

 miles in among the hills, with no kindred rocks or 

 stones near it. It was evidently far from home, but 

 what its means of transportation had been I could 

 only conjecture. 



Amid the flock of gray and brown boulders that 

 55 



