WHITE.] GREEN EIVER VALLEY. 17 



ern corner of the district. Along this portion of its course it runs in a 

 very narrow valley bordered by hills, the most of which are composed 

 of strata of the Fox Hills Group. From the eastern border of the dis- 

 trict to the confluence of a small branch that flows from near the eastern 

 end of Axial Basin, its course is nearly parallel with and upon the 

 north side of an anticlinal axis which produces upon its southern side a 

 short, irregular line of hogbacks. From the confluence of the branch 

 just mentioned to its own confluence with the Yampa, the course of 

 Williams Fork is northward and through a deep narrow valley or 

 canon. This portion of its valley has been carved out of the strata of 

 the Fox Hills Group, the river running almost directly upon the axis 

 of a comparatively short anticlinal spur that extends northward from 

 the place of blending of the Uinta and Park Eange flexures. 



Millc Greek. — This creek rises by several branches, some of them drain- 

 ing the northern side of Danforth Hills, but the main one rises near 

 the eastern border of the district. It is insignificant in size, but it de- 

 rives importance in this dry region from the fact that it contains per- 

 ennial water. It is also worthy of especial notic^ because, although so 

 small a stream, it affords a good example of antecedent drainage. The 

 principal branch just referred to flows northwestwardly through the 

 eastern end of the eastern portion of Axial Basin, but instead of pur- 

 suing its course westwardly down the basin to join the Yampa where 

 that river enters it, the creek cuts through the bluffs that form the 

 northern side of the basin and flows through a canon carved out of the 

 sandstones of the Fox Hills Group and joins the Yampa where that 

 river is itself running in a similar caQon. 



Geeen Eiver Valley. — Green Eiver being the largest of those 

 streams that unite to make up the great Colorado River of the West, 

 is, properly speaking, the upper portion of that great river itself, and 

 ought not to have received a separate name ; but having received it, 

 custom renders a change impracticable. It is into .Green Eiver that 

 the whole drainage of this district passes, either directly or indirectly; 

 but the river itself traverses only the northwestern corner of the dis- 

 trict, entering it at Island Park and leaving it about midway of the 

 western boundary. This portion of the river's course is quite tortuous, 

 and it passes through one remarkable canon, that of Split Mountain; but 

 below this it passes through a broad open valley. 



Island Park lies in the sag or dipping synclinal between Split Moun- 

 tain and the main fold of the Uinta Uplift, and is thus bounded by high 

 mountains on all except the western side. The park may be said to 

 contain about ten square miles, but the amount of irrigable land within 

 its limits is very much less ; still, there is sufficient for the purposes of 

 a small farming neighborhood, whenever it may be desired by settlers. 

 The river here divides into several channels, and, quickly uniting, sev- 

 eral small islands are formed, from which the park has received its 

 name, and which add a feature of beauty to that small, secluded dis- 

 trict. 



Split Mountain Canon. — As Green Eiver makes its exit from one of 

 its great canons through the Uinta Mountains immediately upon enter- 

 ing Island Park, so it enters another great canon, that of Split Moun- 

 tain, immediately upon leaving the park. Split Mountain, as has already 

 been shown, is a large mountain spur from the western end of Yampa 

 Plateau, and it has received this name because it is cleft entirely 

 through, and from top to base, by the canon. The walls of the canon 

 are everywhere precipitous and in large part perpendicular, and are 

 composed of Carboniferous limestones and sandstones. Its length is 

 2 G 



