CHAPTER II. 



SURFACE GEOLOGY — GRAND RIVER AND ITS TRIBUTARIES. 



Grand Eiver rises in Grand Lake, in the northeast corner of Middle 

 Park, west of Long's Peak, aud derives its supply of water near its head 

 from the Colorado or Front Eange, the divide between Middle and North 

 Parks and the Park range. 



It unites with the Green Eiver to form the Colorado, and has a total 

 length of about three hundred aud fifty miles, of which one hundred and 

 fifteen miles is in our district. It rises farther eastward than any other 

 water in Colorado which flows into the Pacific. 



On some maps the name Blue Eiver is given to it, while the name 

 Grand is applied to the Gunnison and to the Grand proper below the 

 mouth of the Gunnison. Gunnisou* callsitNah-un-kah-reaorBlueBiver, 

 and the Gunnison he names the Grand. Blue Eiver, in reality, is in Mid- 

 dle Park and a branch of the Grand. 



The reasons for using the name Grand in preference to'Blue are briefly 

 as follows : 



It is really the main stream, being, at the junction of the Gunnison, 

 twice the size of the latter, and if the name is given to the lower portion 

 it should also be given to the largest stream above. Again, it is so 

 known all through Colorado and at its head in Middle Park, and will 

 probably, therefore, always hold good, while the name Blue is restricted 

 to the branch rising in the divide between the Middle Park and the 

 South Park, and flowing northward along the eastern side of the Park 

 range. 



In Middle Park Grand Eiver is from forty to fifty miles in length, and 

 has been fully described by Mr. Marvine in his report for 1873, and 

 from the Park range to the mouth of Eagle Eiver, a distance of about 

 forty-five mile'? in a straight line, it lies within his district for 1874, and 

 will no doubt be fully reported on by him. 



From the mouth of the Eagle to the mouth of the Gunnison, it formed 

 the boundary between the northern and middle districts, and we have 

 therefore to treat here only of the general features and geology of its 

 southern drainage in this part of its course. There are three large 

 branches which I will take up in their order, commencing at the mouth 

 of the Eagle. 



On glancing at the map we notice that there are two general courses 

 for the streams, the Grand flowing south of west and turning more and 

 more to the southward as we go west, until at one point it flows almost 

 due south, afterward turning to the west before reaching the mouth of 

 the Gunnison. The courses of the main branches, especially of the 

 first two, are west of north. The third holds the same general course at 

 first, but are afterward modified by circumstances that will be explained 

 farther on. 



'Pacific Railroad Report, vol. ii. 



85 



