240 COSMOS. 



The volcano of Tollma:* 18,143 feet, according to a trigonomet- 

 rical measurement by Humboldt. 



The volcano of Arequipa :f 18,883 feet, according to a trigonomet- 

 rical measurement by Dolley. 



* I measured the truncated cone of the volcano of Tolima, situated 

 at the northern extremity of the Paramo de Qnindiu, in the Valle del 

 Carvajal, near the little town of Ibague, in the year 1802. The mount- 

 ain is also seen at a great distance upon the plateau of Bogota. At 

 this distance Caldas obtained a tolerably approximate result (18,430 

 feet) by a somewhat complicated combination in the year 180(5 ; Sema- 

 nario dc la Neuva Granada, nueva edition, aumentada por J. Acosta, 1849, 

 p. 349. 



f The absolute altitude of the volcano of Arequipa has been so 

 variously stated that it becgmes difficult to distinguish between mere 

 estimates and actual measurements. Dr. Thaddaus Hanke, of Prague, 

 the distinguished botanist of Malaspina's voyage round the world, as- 

 cended the volcano of Arequipa in the year 1796, and found at tho 

 eummit a cross which had been erected there twelve years before. 

 By a trigonometrical operation Hanke found the volcano to be 3180 

 toises (20,235 feet) above the sea. This altitude, which is far too 

 great, was probably the result of an erroneous assumption of the ele- 

 vation of the town of Arequipa, in the vicinity of which the operation 

 was performed. Had Hanke been provided with a barometer, a bot- 

 anist entirely unpracticed in trigonometrical measurements would 

 certainly not have resorted to such means after ascending to the sum- 

 mit. The first who ascended the volcano after Hanke was Samuel 

 Curzon, from the United States of North America (Boston Philosophic- 

 alJournal, 1823, November, p. 168). In the year 1830 Pentland esti- 

 mated the altitude at 5600 metres (18,374 feet), and I have adopted 

 this number (Annuaire du Bureau des Longitudes, 1830, p. 325) for my 

 Carte Hypsomctrique de la Cordillere dcs Andes, 1831 . There is a satis- 

 factory agreement (within ^-th) between this and the trigonometrical 

 measurement of a French naval officer, M. Dolley,. for which I was 

 indebted in 1826 to the kind communication of Captain Alphonse dc 

 Moges in Paris. Dolley found the summit of the volcano of Arequipa 

 (trigonometrically) to be 11,031 feet, and the summit of Charcanil 1,860 

 i'eet above the plateau in which the town of Arequipa is situated. If 

 now we fix the town of Arequipa at 7841 feet, in accordance with the 

 barometrical measurements of Pentland and Rivero (Pentland, 7852 

 feet in the Table of Altitudes to the Physical Geography of Mrs. Som- 

 erville, 3d ed., vol. ii., p. 454; Rivero, in the Memorial de Ciencias 

 Naturales, t. ii., Lima, 1828, p. 65 ; Meyen, Reiseum die Erdc, Theil. 

 ii., 1835, s. 5),. Dolley 's trigonometrical operation will give for the 

 volcano of Arequipa 18,881 feet (2952 toises), and for the volcano 

 Charcani 19,702 feet (3082 toises). But Pentland's Table of Alti- 

 tudes, above cited, gives for the volcano of Arequipa 20,320 English 

 feet, 6190 metres (19,065 Paris feet) ; that is to say, 1945 feet more 

 than the determination of 1830, and somewhat too identical with 

 Hanke's trigonometrical measurement in the year 1796 ! In opposi- 

 ffon to this result the volcano is stated, in the Anales dc la Universidad 

 de Chile, 1852, p. 221, only at 5600 metres, or 18,378 feet: consequent- 

 ly 590 metres lower! A sad condition of.hypsometry ! 



