38 TRAVELS AMONGST THE GREAT ANDES, chap. ii. 



on the northern side of the Arenal^ at the base of the mountain, 

 and proposed that on the first day we should not try to go 

 farther. 



The needle of Aneroid F pointed to 15*370 inches when the 

 Carrels were at the place that they selected for the higher 

 camp, and as the corresponding figures on the '^ scale of feet"' 

 were 19,122 they could have fairly claimed to have reached that 

 height '^ by aneroid.^' I estimated that they had only got about 

 as high as 16,450 feet. The Aneroid F, at all stages of the 

 journey, read lotver' than the mercurial barometers. At Guaya- 

 quil its error was — 0*172 ; at Muiiapamba it was —0*208 ; at 

 Tambo Gobierno it was —0*629 ; and, upon arrival at Guaranda, 

 — 0*708 of an inch.^ Its error constantly increased. When 

 they left Guaranda on Dec. 21 it amounted to —0*890 of an 

 inch, and on their return upon the 23rd it had risen to — 1*080 

 inches. I assumed that the error was regularly increasing, and 

 that when they reached their highest point, soon after mid-day 

 on the 22nd, it amounted to one inch. In that case, the true 

 barometric reading would be 16*370 inches. 



The figures corresponding with 16*370 inches upon the 

 ^^ scale of feet'" were 17,400, but from this amount I subtracted 

 950 feet, for the following reason. Aneroid F (like a great 

 part of the aneroids which are in use) had its zero, or level of 

 the sea, at 31 inches, and made 30 inches correspond with a 

 height of 894 feet above the sea.^ I assumed that atmospheric 

 pressure at the level of the sea on Dec. 22 was a little less 

 than 30 inches,^ and deducted 950 feet accordingly. This 



1 It should not be supposed that this was due to bad graduation, I had seen 

 this aneroid, like all the others when tested under the an-pump, accord inch by 

 inch with the attached mercurial barometer. 



^ See How to use the Aneroid Barometer, pp. 56-7. 



2 This could be assumed with some probability, as the variations in atmospheric 

 pressure are small in Ecuador. See Appendix B. 



Upon return to Guayaquil, I found that Mr. Chambers had recorded 29957 

 inches (mere. bar. reduced to 32°) as the reading at 11 a.m. on Dec. 22. 



