COMPARATIVE HEIGHT OF MOUNTAINS. 13 



EUROPE. 



Height 

 Names Country where situate. in English feet 



29 Mount Perdu . . Pyrenees 11,209 



30 Etna (Volcanic) Sicily . Sicily 10,963 



31 Olympus . . . Greece 6,600 



32 Vesuvius (Volcanic) . Naples i 3,978 



33 Hecla (Do.) . . . Iceland 3,690 



34 Stromboli . . . Lipari . . , . . . 3,020 



35 Gibraltar . . . Andalusia . . . . . 1,439 



36 Montmartre . . . Paris 400 



37 Ben Nevis . . . Invernesshire .... 4,358 



38 Snowdon . . . Carnarvonshire .... 3,571 



39 Ben Lomond . . Stirlingshire . . .f . . 3,240 



40 Skiddaw . / . '" . $ Cumberland , 3,055 

 The great pyramids of Egypt and St. Paul's Cathedral are thelower figures. 



MODES OF ASCERTAINING THE HEIGHTS OF MOUNTAINS. 



The height of mountains exercises an important influence on the climate 

 and productions of the regions where they occur, and it becomes an 

 important point to determine their respective altitudes. This has usually 

 been attempted by two methods ; by geodesical mensuration, and by 

 marking the difference of the barometrical columns on their summits, 

 and at their bases. The first is the most accurate, when we can obtain a 

 level base at a moderate distance from the height to be ascertained, and 

 when the measurements of the angles are carefully taken by expert opera- 

 tors, and with good trigonometrical instruments. The use of the baro- 

 meter is confined to accessible heights, but it is much more easily 

 managed under such circumstances, and requires little more than atten- 

 tion to the true height of the barometrical column, corrected for the 

 temperature of the instrument, and of the ambient air. In variable 

 climates, accuracy would require synchronous observations at the foot 

 and on the summit of the height to be ascertained ; but in tropical 

 climates, or even in the South of Europe, the barometer scarcely varies 

 throughout the year, at the level of the sea, and therefore such measure- 

 ments are more easily made. An instrument invented by the Rev. 

 F. Wollaston has been used to measure great elevations, by marking the 

 temperature at which water boils at the base and the summit. This, 

 though an ingenious instrument, is so liable to accidents in carriage, that 

 it isseldom used. 



