APPENDIX A 319 



after noon. The direction used in the azimuth observation was also taken 

 with the prismatic compass. The mean of the magnetic declination thus 

 found is: East 8° 30' plus. 



Observations for latitude were taken to the sun by the method of 

 circum-meridian altitudes, except at the town of Vilcabamba where star 

 observations were taken. 



As a matter of course, observations to the sun are not so exact as star 

 observations, especially in low latitudes where one can expect to observe 

 the near zenith. However, working in high altitudes for long periods, 

 moving camp every day and often arriving at camp 2 to 4 hours after 

 sunset, I found it essential to have undisturbed rest at night. It was 

 beyond my capacity to spend an hour or two of the night in finding the 

 meridian and in making the observation. Furthermore, the astronomic 

 observations were to check the topography mainly, the latter being the 

 most exact method with the outfit at hand. 



The following table contains the comparisons between the latitude sta- 

 tions as located on the map and by observation : 



Map Observation 



Camana Quadrangle S 16° 37' 34" 16° 37' 34" * 



Coropuna, station 9,691S 15° 48' 30" (15° 51' 44") 



Cotahuasi, " 12,588S 15° 11' 40" 15° 12' 30" 



La Cumbre, " 16,852S 14° 28' 10" 14° 29' 46" 



Lambrama, " 8,341S 13° 43' 18" 13° 43' 14" 



The other observations, with the exception of the one on the Coropuna 

 Quadrangle, check probably as well as can be expected with the small and 

 light outfit which we used, and under the exceptionally hard conditions of 

 work. The observation on the Coropuna Quadrangle just south of 

 Chuquibamba is, however, too much out. An explanation for this is that 

 the meridian zenith distance was 1° 23' 12" only (in this case the exact 

 formula was used in computing) . Of course, an error or an accumulation 

 of errors might have been made in the distances taken by the micrometer- 

 alidade, but the first cause of error mentioned is the more probable, and 

 this is indicated also by the fact that the location on the top of Mount 

 Coropuna checks closely with the one determined in an entirely independent 

 way by the railroad engineers. 



For the cross-section map from Abancay to Camana, the following 

 statistics are desirable : 



1 The observation at Camana checks very closely with a Peruvian observation the 

 value of which is S. 16° 37' 00". 



