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Sierra Club Bulletin. 



fine volcanic ash. South of Pumice Flat the trail passes 

 between the Devil's Postpile and the river, and then joins 

 the main Mammoth Trail, which connects the settlements 

 near Wawona and Summerdale with Long Valley on the 

 eastern slope. 



The Devil's Postpile is a wonderful cliff of columnar 

 basalt facing the river. The columns are quite perfect 

 prisms, nearly vertical, and fitted together like the cells 

 of a honeycomb. Most of the prisms are pentagonal, 

 though some are of four or six sides. The standing col- 

 umns are about two feet in diameter and forty feet high. 

 At the base of the cliff is an enormous pile of these pris- 

 matic fragments. The cliff facing the river furnishes the 

 best example of this columnar basalt structure, but wher- 

 ever the bedrock is exposed beneath the pumice covering 

 the same formation can be seen. 



Joining the Mammoth Trail and following it east about 

 a mile, we come upon Reds Meadow. This is an ideal 

 camping-spot — a fine luxuriant meadow fringed with 

 splendid forest. Through it flows several clear rushing 

 streams well stocked with trout, and a fine hot spring 

 bubbles out of the hillside near by. From Reds Meadow 

 the Mammoth Trail passes easterly over the Sierra sum- 

 mit, down past the Mammoth Lakes and mine to the 

 Mineral Park settlement and out on the desert plains 

 toward Owens River. 



Following the San Joaquin River down about one and 

 one-half miles below the Mammoth Crossing, we come 

 upon the Rainbow Fall. This fall is formed by the entire 

 volume of the Middle Fork pouring in a smooth broad 

 sheet over a ledge of volcanic rock into a box cafion. 

 The height of the fall is about one hundred and forty feet, 

 its width perhaps ninety feet when the stream is in flood, 

 and the drop is absolutely vertical. Both this and the 

 Devil's Postpile are included in the recently established 

 National monument. The area set aside is rectangular in 

 form, one-half mile wide east and west and two and one- 

 half miles long north and south. 



