288 



THE HEIGHT OF THE BARRIER AND THE SOUTH POLAR PLATEAU. 



Heights on the Beardmore Glacier. 



The barometer used by the Polar Party was compared during the ascent of the Beardmore 

 Glacier 24 times with a hypsometer, the mean correction found was --05". As the hypso- 

 raeter was broken before the top of the Beardmore was reached, the comparisons could 

 not be continued throughout the journey. The barometer had been set to be correct when 

 leaving Cape Evans, and as it did not return for recomparison it has been assumed that 

 the small change of -05" found by the hypsometer tests was real and this value has 

 been used throughout. The barometer thus corrected agrees well with other barometers which 

 were being read by other parties in its neighbourhood. 



For purposes of the calculation of heights the journey from the Barrier to the Pole 

 and back will be divided into four parts, namely : — 



(1) From Pony Depot on the Barrier to Mid-Glacier Depot. 



(2) From Mid-Glacier Depot to Upper Glacier Depot. 



(3) From Upper Glacier Depot to 3° Depot. 



(4) From 3" Depot to the Pole.* 



In the first three intervals the method of determining the height was as follows : When 

 going from A to B the last barometer reading at A and the first at B were extracted from 

 the meteorological register and the mean temperature in the interval determmed. From these 

 the difference of height was calculated as though the pressure observations had been made 

 simultaneously. 



As there was usually several days between the actual observations it was necessary to 

 correct for any general change of pressure during the interval. To do this the pressure and 

 temperature at Cape Evans were taken for the same times and from these the equivalent 

 change in height was calculated. It was then assumed that the whole of the atmosphere 

 had been raised or depressed by this amount so that this value was apphed as a correction 

 to the observations made on the Beardmore. Luckily there were no large pressure changes 

 durin'^ the peiriod the Polar Party was on the Glacier so that this correction is always small 

 and therefore any error in the assumption is of subordinate importance. An example will 

 indicate the method. 



Detailed Calculation of the heigJit between the Barrier and Mid-Glacier Depot. 



Polar Party Outward. 



Date. 



December 9th. 



6 hrs. 

 December 17th, 



19 hrs. 



Fony Depot 

 Mid-Glacier Depot 



Pressure. 

 29-65 1 

 •JU'lsf 



Change. 

 3-47 



Ditference 

 Temperature correction 



Cape Evans 

 pressure. 



December 9th. 



6 hrs. 

 December 17th, 



19 hrs. 



29-96 1 

 20-76/ 



Mean 

 temperature. 



23°F. 



Approximate height 

 table 20. 



- 55 

 + 128 



Temperature correction ... 

 Error due to pressure change 



182 

 9 



173 



Mean temperature 



•20'F. 



Approximate height 

 from table 20 

 Smithsonian Tables 

 228 

 3,6U 



3,3S3 



- 207 



3,176 

 - 173 Correction for 

 pressure change. 



3,003 



Ditference 

 height. 



Temperature correction 

 from table 21 

 Smithsonian Tables 

 3,0U0 feet - 184 

 300 „ - 18 



80 „ - 5 



207 



* For geographical positions, see table 152, page 291, 



