1890.] XATUHAL SCIENCES OF PHILADELrillA. 



Tables of Delcros : 



Difference of barometric values . 

 Addition for temperature . 

 Correction for latitude (deer, grav.) . 

 Correction for gravity (vertical) 

 Correction for elevation of lower station 



253 



3117.7 metres. 

 173.6 •' 



7.4 " 

 10.0 " 



2.5 " 



Elevation of the Mexican Observatory 

 Elevation above point of observation 



Allowance for drop of .1 barometer 



Tables of Guyot : 



Difference of barometric values 

 Addition for temperature 

 Correction for latitude (deer, grav.) 

 Correction for gravity (vertical) 

 Correction for lower station 

 Elevation of Mexican Observatory . 

 Elevation above point of observation 



Allowance for drop of .1 barom. 



3311.2 

 10,863.3 English feet. 

 7403.0 " 

 120.0 



18,386.3 

 180.4 



10,232.9 



563.0 



22.5 



34.0 



7.5 



7403.0 



120.0 



18,382.9 



178.4 



18,206 

 feet. 



18,204 



This determination of the height of Orizaba is considerably above 

 the values which have heretofore been given for the mountain. 

 Ferrer, in 1796, by means of angle measurements taken from the 

 Encero, determined its height to be 17,879 feet. ^ Humboldt, a few 

 years later, measured the mountain from a plain near the town of 

 Jalapa, and obtained only 17,375 feet,^ but he observes with char- 



^ Humboldt, Cosmos, V, p. 252, Bohn's Edition. I have not been able to 

 find the orginal account of this measurement, but there is a brief note, entitled 

 " Height of some Mountains in New Spain," and published by Ferrer in the 6th 

 volume of the Transactions of the American Philosophical Society (p. 164), in which 

 the height here slated (or its equivalent, 1:795 toises) is given. 



2 Op. cit., V, p. 252. 



