120 



DETERMINATION OF ALTITUDES BY BAROMETER. 



The following example is introduced to illustrate the method of computation above described : 



EXAMPLE. 

 Data for determining the altitude of Camp 22, near upper end of upper canon of Pit river. 



Corrections applied before computation. 



Barometric reading 



Correction for temperature of mercury. 



Correction for instrumental errors 



Correction for horary oscillation 



Correction for abnormal oscillation 



6 p. m., August 7. 



Bar. 1060. 



Corrected readings. 



Inches. 

 25. 990 

 —.112 

 .000 

 +.020 

 +.075 



25.973 



Bar. 1089. 



Inches. 

 25. 957 

 —.112 

 +.044 

 +.020 

 +.075 



25. 984 



9 p. m., August 7. 



Bar. 1060. Bar. 1089 



Inches. 

 25. 990 

 —.081 

 .000 

 —.004 

 +.075 



25.980 



Inches. 

 25. 953 

 — . 0S1 

 +.044 

 —.004 

 +.075 



25. 987 



6 a. m., August 8. 



Bar. 1060. Bar. 1089 



Inches. 

 26.025 

 —.045 

 .000 

 —.040 

 +.040 



25. 980 



Inches. 

 25.981 

 —.044 

 +.044 

 —.040 

 +.040 



25. 981 



Mean of corrected readings, 25.981 inches. 



Mean daily air temperature, about 67° Fahrenheit. 



Computation by Loomis' tables. 



H = 30. 057 

 t — 64° 



H' = 25.981 



e = 67° 



Part I gives for 



C H = 30.057 

 I H' — 25. 981 



27659.2 

 23851. 8 



Approximate altitude a 380.7. 4 



a , „,, 3807.4 



9-00 (< + < " 64) =-900- X " 283 " 4 



Second approximate altitude A 4090.8 



Part III gives for A = 4090.8 and L = 41° 50' 1.8 



Part IV gives for A =r 4090. 8 11. 1 



Altitude of station in feet 4103. 7 



