258 Prof. Bischof ati the Temperature of 



that the snow was in such a state as to be about to melt. So 

 far, then, it is certain that, at the highest points of our globe, 

 there are still variations in the temperature of the air. Whe- 

 ther this disappears at the height of 34,158 feet, as Von Lin- 

 denau* supposes, must remain a question. 



But the variations in the temperature of the soil disappear 

 in accessible heights, even at a small depth beneath the surface. 

 According to Boussingault''s observations (Chap. VIII), in the 

 Cordilleras, the temperature of the soil is there constant even 

 at a depth of one foot, on the level of the sea. As in higher 

 latitudes the depth to which the influence of the external tem- 

 perature penetrates, is much greater than between the tropics 

 (Chap. VIII.), the same must also be the case at all heights ac- 

 cessible to man. 



According to the observations which I have been making for 

 a year past, in front of the chemical laboratory and on the top 

 of the Lowenburg, situated 1173 feet higher, the yearly varia- 

 tions of the temperature of the earth at the depth of four feet, 

 amount, at the former place, to 19°.12, and at the latter to 

 15°.63. For reasons which will be given below, I think, that 

 the yearly variations of temperature on the Faulhorn, 8178 feet 

 above the sea, and 6784 feet above the Lowenburg, are not less 

 considerable at a depth of four feet. It is, however, to be ex- 

 pected, that at the higher points of the Alps, where the earth 

 is covered with perpetual snow, the temperature of the soil at 

 this depth below the surface is constant. 



Can the decrease of temperature with the height be consi- 

 dered as an arithmetical progression in the strictest sense of the 

 word ? 



Von Humboldt's observations, according to which, the differ- 

 ence of height corresponding to 2°.ii5 difference of temperature 

 is greater, the greater the difference of height between the two 

 points of observation, seem indeed to indicate, that between 

 the tropics the decrease of temperature becomes less and less 

 rapid from the level of the sea nearly to the regions of perpe- 

 tual snow. And Humboldt-f himself doubts whether this de- 



• Monatliche Correspondenz, xxL, 119. See Ideler, p. 103. 

 t Gilbert's Annal. xxiv. p. 48. 



