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 wasa 
water-worn mass of metamorphic rock, nearly as 
high as my head, at the end of a valley, 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 
