490 GEOLOGICAL SURVEY OF THE TERRITORIES. 



tern. After a number of experiments on different methods it was found 

 that to bring order out of this chaos, it was necessary to take up each 

 link in the chain separately,' and use all the data that could be found 

 pertaining to it, and determine the difference of level of these two sta- 

 tions finally. Next, the same process had to be gone through with the 

 liue from the second point to the next station beyond, and so on. In 

 doing this it was found that some of these lines were much better deter- 

 mined than the others. In finally reducing these differences of level 

 to a commou datum point, this fact might multiply the errors in the 

 work. For instance, a number of well-determined differences of level 

 might be transferred through a poorly determined line, thus vitiating 

 all with the error of the one. In order to obviate this the following 

 scheme was adopted: A central chain of well-determined lines was car- 

 ried through the heart of the mountain-mass from Mount Wilson, the 

 most westerly of the high peaks, to station 8, five miles east of Uncompah- 

 gre Peak, in the northeast corner of the mass. From this main line sev- 

 eral secondary branches were carried wherever the short lines could be 

 well determined. This system covered the whole mass of mountains. 

 Other stations, which could not be well enough determined independ- 

 ently, were connected with different points in the main lines. In the 

 central line we have the following parts: From Mount Wilson to sta- 

 tion 30, a peak east of it and distant 9.3 miles, is a fall of 383 feet, which 

 is the mean of five determinations having a range of 32 feet; thence 

 east to Sultan Mountain, a distance of 6.88 miles, with a fall of 536 feet, 

 the mean of six determinations, range 23 feet ; thence northeast to sta- 

 tion 16, distant 6.60 miles, a rise of 175 feet, the mean of nine determi- 

 nations, range 35 feet; thence northeast to Handle's Peak, 7.51 miles, 

 a rise of 456 feet, the mean of eight determinations, range 54 feet; thence 

 north to Uncompahgre Peak, distant 11.14 miles, a rise of 238 feet, the 

 mean of nine determinations, range 49 feet ; thence east to station 8, 

 distant 4,92 miles, a fall of 1,380 feet, the mean of ten determinations, 

 range 67 feet. This completes the central or trunk line, whose length 

 is 46.35 miles. From Sultan Mountain a branch was extended eastward ; 

 from this peak to station 25, distant 10.28 miles, a rise of 209 feet, the 

 mean of twelve determinations, range 67 ; thence to Eio Grande Pyra- 

 mid, distant 8.63 miles, a rise of 197 feet, the mean of nineteen determi- 

 nations, range 95. 



From station 25, a branch extends to Mount Oso, distant 7.29 miles, 

 a rise of 64 feet, the mean of seven determinations, range 37. 



From station 30 a secondary branch was extended south and west. 



Station 30 to Engineer Mountain, distant 6.98 miles, a fall of 926 feet, 

 the mean of eight determinations, range 22; thence west to station 36, 

 distant 6.76 miles, a fall of 417 feet, the mean of eleven determinations, 

 range 51 ; thence to station 37, distant 3.65 miles, a rise of 94 feet, the 

 mean of five determinations, range 35. 



Another important sub-line extends from Sultan Mountain to the 

 northwest. The first link in the chain is the line from this point to 

 station 28. The heights of stations 30 and 16, above Sultan Mountain, 

 having been already well determined from the central chain, I made use 

 of all the connections between station 28 and each of these points, re- 

 ducing all of them to a common point. The result from this was the 

 following : Sultan Mountain to station 28, distant 7.86 miles, a fall of 

 484 feet, the mean of eighteen determinations, range 76 feet; thence to 

 station £9, distant 3.77 miles, a rise of 324 feet, the mean of eight de- 

 terminations, range 43 feet ; thence to Mount Sneffels, distant 5.94 

 miles, a rise of 952 feet, the mean of six determinations, range 36 feet ; 



