98 



Sierra Club Bulletin. 



Three essential elements must be considered in baro- 

 metric hypsometry : temperature^ pressure, and vapor- 

 pressure, and the observations should be taken at different 

 times of the day and on different days, so as to obtain a 

 true mean ; an error of one degree in mean temperature 

 causes an error of twenty feet in the height of Mt. Whit- 

 ney; an error of .001 of an inch in pressure causes an 

 error of one foot in the computed height. In these obser- 

 vations the attached thermometer is read for temperature 

 and there are no hygrometric observations; then again 

 the temperature at Independence, etc., was taken from 

 the thermograph, so that a possible error of from one hun- 

 dred to two hundred feet is not improbable. 



From the data available, using your formula in your 

 Barometry Report, I make the height of Mt. Whitney as 

 follows : 



By using the simultaneous observations taken by 

 the observer at Independence and by Professor Feet. 



McAdie at Mt. Whitney, the elevation is 14,651 



San Francisco and Mt. Whitney 14,532 



Mt. Tamalpais and Mt. Whitney 14,618 



Mean 14,600 



If we reduce the observations at Independence, San 

 Francisco, and Mt. Tamalpais to sea-level, and then com- 



pute to Mt. Whitney, we have — ^ ^ 



Independence and Mt. Whitney 14,590 



San Francisco and Mt. Whitney 14,532 



Mt. Tamalpais and Mt. Whitney 14,595 



Mean 14,572 



or a difference of twenty-eight feet from the preceding. 



Professor McAdie, using observations taken at San 

 Francisco only, calculates the height at 14,515. 



