302 REPORT UNITED STATES GEOLOGICAL SURVEY. 



7.86 miles, a fall of 484 feet, the mean of eighteen determinations, range 

 7G feet ; tlience to Station 9, distant 3.77 miles, a rise of 324 feet, the 

 mean of eight determinations, range 43 feet ; thence to Mount Sneffels, 

 distant 5.94 miles, a rise of 952 feet, the mean of six determinations, 

 range 36 feet ; thence to Station 34, distant 6.65 miles, a fall of l,16l 

 feet, the mean of five determinations, range 23 feet. This completes all 

 the well-determined chains. Other stations on which barometric read- 

 ings have been taken were connected with as many points in the main 

 lines as possible, and these being reduced to a common point, a mean 

 was taken. Such points are the following : Sultan Mountain to station 

 10, a fall of 223 feet, the mean of eleven determinations, range 76 feet; 

 Uncompahgre Peak to Station 5, a fall of 1,498 feet, the mean of ten de- 

 terminations, range 85 feet ; Uncompahgre Peak to Station 11, a fall of 

 3,624 feet, the mean of eight determinations, range 111 feet ; Sultan 

 Mountain to Station 51, a fall of 835 feet, the mean of three determina- 

 tions, range 75 feet; Sultan Mountain to Station 48, a fall of 1,061 feet, 

 the mean of six determinations, range 59 feet ; Handle's Peak to station 

 13, a fall of 1,175 feet, mean of fore and back sights, range 6 feet. Be- 

 sides these, there are two which depend on single determinations. 

 First, from Sultan Mountain to the point in Baker's Park where the 

 road crosses Cement Creek in Silverton, distant 3 miles, a fall of 3,961 

 feet ; second, from Mount Sneffels to Station 32, which is obtained from 

 sights to a common point between them, distant from Mount Sneffels 

 2.04 miles, and from Station 32, 3.75 miles, the fall is 5,050 feet. This 

 difference of level is checked by sights to distant points to the south of 

 ' Station 32. These two cases are admitted because the distances were 

 so short as to preclude the possibility of any considerable error. From 

 tliese results a table was made out showing the heights of each station, 

 above or below a common datum point. Sultan Mountain was selected 

 as the datum point from its central location, and also from the fact that 

 it was situated on the great central chain of levels, at its junction with 

 two principal sublines. A second column was added, giving the height 

 of each station as determined by the single barometric reading taken 

 thereon. A third column was made out of the first two, by adding the 

 number in the first column to the one in the second when preceded by the 

 minus sign, and by subtracting it when plus. This column represents the 

 elevations above sea-level of Sultan Mountain as determined from the 

 barometric readings at the several stations. It will be seen that the 

 twenty-three results have a range of 203 feet. A mean of all these was 

 assumed as the true height of Sultan Mountain; and by reversing the 

 previous process and adding the plus differences of height in the first 

 column and subtracting the minus, a fourth column was obtained, giving 

 the elevation of each station as reduced from the mean of the twenty-three 

 readings. A fifth column was added, giving the date of each reading on 

 the different stations. From this it will be seen that the observations 

 extend from August 1 to October 6 — more than two months. By exam- 

 ining the table carefully it will be seen that nearly all the earlier read- 

 ings give heights above the mean and the latter below it. Whether this 

 is merely acci|iental, or due to some physical law, I cannot tell. It will 

 be seen that several of these stations, whose height relative to the rest 

 has been well determined, do not appear in the table. This is due to the 

 fact that at those stations, either from storms or other causes, we failed 

 to get barometric readings. 



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