190 J. D. Dana — Rocky Mountain Protaxis and the 



The style of marking for the several formations will be 

 learned by following the series of areas along the railroad 

 southeastward from above Weber to Echo Canon and thence 

 to the Uinta Mountains : the Cambrian C, black with fine 

 white lines ; Silurian S, finely cross-lined (always adjoining 

 the Cambrian) ; Devonian D, dotted ; Carboniferous Cb 1 , Cb a , 

 Cb 3 , corresponding to the divisions mentioned above except 

 that the Permian is included in Cb 3 ; Triassic Tr, marked by 

 Ts ; Jurassic J, finely lined, and crossed by heavy lines ; Cre- 

 taceous, Cr 1 , Cr 2 , Cr 3 , Cr 4 , corresponding to the subdivisions of 

 the Cretaceous above stated, the last, which is the Laramie, 

 being finely cross-lined. 



The Archaean areas are marked with small Ys ; and regions 

 of trachytic eruptions, by the letter/' as stated above. 



The only liberty taken with the original map by the writer 

 is the insertion of dotted lines to indicate the continuations 

 between the disjoined parts of areas. These on the neck 

 between the Uinta and Wasatch Mountains are indicated by 

 the section at the bottom of the original map as well as by the 

 outcropping areas within the neck ; and the others are plain 

 folio wings of the map and the text, except for the Lower Cre- 

 taceous area north of the northwest part of the Uinta Moun- 

 tains. If regarded as doubtful beyond this, they are to be 

 taken as the writer's suggestions. 



We come now to the orographic facts. 1. Along the western 

 wall and summit of the Wasatch, the larger Archaean areas 

 are numbered 1, 2, 3, 4 ; 1 is the most northern ; 2 is east of 

 Ogden ; 3 commences abreast of Uinta and continues for about 

 25 miles ; 4 has its summit in Lone Peak, 11,295 feet in 

 height. Just east of the last there is the isolated Clayton 

 Peak (marked by Ys on the map) 11,889 feet high. 



The Wasatch Mountains commence to rise on the north, 

 abreast of a broad synclinal of Paleozoic rocks from Cambrian 

 to Carboniferous, the east part of which is a continuation of 

 the Bear Lake Eange, 9,000 to 10,000 feet in height. Other 

 isolated Archaean ridges occur north of and within Salt Lake. 



The general dip of the Paleozoic formations in the moun- 

 tains is eastward from 60° to 25°. The line of strike of the 

 outcrops is peculiar in having large in-and-out bends along the 

 range, as is easily seen by following the black-lined areas of 

 the Cambrian ; there is a bend eastward to the Weber region, 

 and then a profound bend westward through the gap nearly 

 18 miles wide between the Archaean ridges 3 and 4, abreast of 

 Salt Lake City, making a synclinal in the squeeze through the 

 gap, whose broken-off head overhangs and confronts the Salt 

 Lake Yaliey ; then another eastward sweep of more than a 

 semi-circle around " Lone Peak " first the Cambrian and then 



