CHAP. XIX 







PRESSURES 1 



Number Atmospheric pressure 

 of nights. experienced. 



4 . . 29-000 -28-500 inches 



4 





. 23-600 -22-540 „ 



30 





22-510-21-900 „ 



90 





21-720-21-110 „ 



6 





20-920-20-200 ,, 



15 





19-800-19-500 „ 



14 . 





19-270-18-900 ., 



13 





18-755-18-280 ,, 



4 







18-080-17-780 „ 



4 







17-730 



1 







17-410 



5 







17-430 



1 







17-250 



1 







17-220 



2 







16-950 



1 







16-840 



10 







16-500 



6 







16-000 



1 







14-750 



371 



Height above level of sea. 



Less than 6000 feet. 

 Between 6000-8000 feet. 



do. 



8000 - 9000 



do. 



9000 - 10,000 



do. 



10,000-11,000 



do. 



11,000-12,000 



do. 



12,000-13,000 



do. 



13,000 - 14,000 



do. 



14,000-14,500 





At 14,762 





do. 14,992 





do. 15,189 





do. 15,207 





do. 15,446 





do. 15,811 





do. 15,984 





do. 16,664 





do. 17,285 





do. 13,500 



Having recapitulated the various ways in which we were 

 affected whilst among the Great Andes, I now pass on to the question, 

 Can one become habituated to low pressures ? and in connection 

 with this bring together in a tabular form upon page 372 a few 

 examples of the rates of speed that were attained over the longer 

 courses ; selecting them only from instances in which the times 

 occupied were exactly noted and the differences of level were 

 well ascertained, and taking them from those in which we started 

 unexhausted by previous work, from places where atmospheric 

 pressure was already low. 



Without a few words of explanation, not much edification can 

 be obtained from this table. A reader may compare the entry at 

 January 7 with that of June 9 and conclude from the apparent 

 falling -off that there is evidence of deterioration rather than of 

 improvement. This conclusion would be erroneous. The dissimi- 

 larity of the work sufficiently accounts for the difference between 



