206 PHYSICAL GEOGKAPHY. 



Feet. 



Absolute elevation of poplars found by Gerard in the Himalaya, twelve feet in girth . 12,000 



Highest point of road across the Andes . . . . . . . 11, 499 



Elevation of Potosi, the highest city of the globe ...... 13,330 



Elevation of Santa Fe de Bogota . . . . . . . 8,727 



Elevation of the city of Mexico ........ 7,520 



Highest pass in Europe, that of the Cervin, Col du Geant, Alps . . . 11,274 



Highest constructed road in Europe, the pass of the Ortler Spitz .... 9,100 



Pass of the Col de Tende over the Maritime Alps ..... 5,887 



Pass of Mount Cenis over the Graian Alps ....... 6,773 



Pass of the Simplon over the Pennine Alps ...... 6,578 



Highest inhabited spot in Europe, the Inspector's house, pass of St. Maria . . . 9,272 



Hospice of St. Bernard . . . . . . . . . 8,185 



Mine of Real del Monte in Mexico . . . . . . .9,120 



Highest growth of Peruvian bark ....... 9,590 



Highest village of Europe, Soglio, in the Grisons . . . . . .6,714 



Highest habitation of Great Britain, Cavour, a hunting-lodge in the Grampians . 1 , 740 



Highest habitation of England, Allenheads, in Northumberland .... 1,400 



Contemplating the projections of the surface with reference to their absolute elevation 

 above the level of the sea, some of them appear protuberances of enormous bulk, and we 

 are apt to imagine that they must detract largely from the regularity of the earth's 

 spherical form. But they become insignificant when compared with the volume of the 

 globe itself, the highest eminence, that of between five and six miles, being only about 

 g-J-0- of the semidiameter of the sphere. They bear therefore much the same proportion 

 to the terrestrial spheroid as the little risings on the coat of an orange to the fruit. 

 Books of travels abound with conflicting statements respecting the distance from which 

 particular mountains may be seen. The length of the line of visibility is not only 

 influenced by conditions of the atmosphere, but by the character of projections, apart 

 from their height. The Peak of Teneriffe is not so frequently visible at the same 

 distance as those tops of the Andes which are of corresponding elevation, not being, like 

 them, invested with perpetual snow. Humboldt remarks, that the cone of the former, 

 no doubt reflects a great degree of light on account of the white colour of the pumice 

 with which it is covered ; but its height does not form a twenty-second part of the total 

 elevation, and the sides of the mountain are coated with blocks of dark-coloured lava, 

 or with luxuriant vegetation, the masses of which reflect little light, the leaves of the 

 trees being separated by shadows of greater extent than the illuminated parts. He refers 

 therefore the Peak to that class of mountains which are seen at a great distance only in 

 a negative manner, or because they intercept the light transmitted from the extreme 

 limits of the atmosphere. Still, it has been observed at the distance of 124, 131, and even 

 138 miles; and the summit of Mowna-Roa in the Sandwich Islands has been seen, at 

 a period when it was destitute of snow, skirting the horizon from the distance of 183 

 miles. This is the most remarkable example yet known of the visibility of high land, 

 and as Mowna-Roa was negatively seen, both cases refute the theory of Bouguer, that 

 mountains seen negatively cannot be perceived at distances exceeding 121 miles. 



The summits of the superior elevations are regions of perpetual snow and ice, and 

 below the limits of constant congelation there is a zone in which snow lies upon the 

 surface through the greater part of the year. The accumulations above and near the 

 line where perpetual frost commences, constitute some of the most dangerous and terrible 

 phenomena of high mountain districts. When the mass becomes so great that the 

 inclined plane on which it rests can no longer support it, or when the pile which has 

 been heaped together by the winter snow-storms becomes loosened by the action of the 

 sun in spring and summer, it descends with immense violence from its site into subjacent 



