410 AxNAi.s OF THE Carxe(;ie Museum. 



On June 25, 1902, I ascended one of the canons (Taylor) that 

 have their beginnings near the crest of the Ruby Mountains and ex- 

 tend eastward as deep valleys or ravines in the Palaeozoic rocks to the 

 Ruby valley. I copy from my notes : 



" After passing some limestone pillars, showing ])eculiar weathering, 

 I came to the thin-bedded Subcarboniferous limestone [Madison 

 Laminated Limestones] with fossils. In the upper part of the canon 

 the Subcarboniferous is near to the gneiss. On the top the rock 

 is gneiss dipping northeast or between east and north. I turned 

 toward the north, ascending a higher ridge, and finally came to crystal- 

 line limestone. I was anxious to find the relation of this to the gneiss, 

 and so went back perhaps 20 or 30 rods in the gneiss and saved sam- 

 ples" of the different kinds of rock from the gneiss, and then went a 

 long distance up into the crystalline limestone. The limestone is nearly 

 uniform, but with some layers that are different from the main mass. 

 . . . This limestone makes a very high sharp ridge. . . . Above 

 this I found another band of gneiss. I then began down in the lime- 

 stone and saved samples through the band of gneiss, the shales that 

 lie above it, and the Cambrian limestones which were identified by 

 the fossil trilobites which it contained." 



So here we have the following : 



5. Cambrian limestone with trilobites; 



4. Shales (undoubtedly Llathead shales) ; 



3. Gneiss ; 



2. Crystalline limestone ; 



I. Archaean gneiss. 



1 made no measurements, but the narrowest of the divisions is 

 probably not less than 150 to 200 feet in thickness. 



It is probable that the crystalline limestones and a portion of the 

 gneiss here represent the Cherry Creek formation. If it be thought 

 that the upper band of gneiss might be metamorphosed Cambrian 

 rock we would have a sudden change from the highly altered to the 

 unaltered Cambrian Avhich is evidently not due to local Post-Cambrian 

 metamorphism. 



The western portion of the Ruby Mountains in the vicinity of Dil- 

 lon is gneiss, but I have not examined all the area that intervenes be- 

 tween this and the eastern crest just alluded to. 



2 In the collection of the University of Montana. 



