114: COSMOS. 



The solution of the question whether the elevation of the 

 soil does in itself exert a perceptible influence on magnetic 

 dip and intensity, 43 was made the subject of very careful 

 investigation during my mountain journeys in the chain of 

 the Andes, in the Ural, and Altai. I have already observed, 

 in the section on Magnetic Intensity, how very few localities 

 were able to afford any certainty as to this question, because 

 the distance between the points to be compared together 

 must be so small as to leave no ground for suspecting that 

 the difference found in the inclination may be a consequence 

 of the elevation of the soil, instead of the result of the cur- 

 vature of the isodynamic and isoclinal lines, or of some great 

 peculiarity in the composition of the rocks. I will limit 

 myself to the four results which I thought at the time they 

 were obtained, showed more decisively than could be done 

 by observations of intensity, the influence exerted by eleva- 

 tion in diminishing the dip of the needle. 



The Silla de Caracas, which rises almost vertically above 

 La Guayra, and 8638 feet above the level of the sea, south 

 of the coast but in its immediate vicinity and north of the 

 town of Caracas, yielded the inclination of 41. 90 ; La 

 Guayra, elevation 10 feet, inclination 4 2. 20 ; the town of 

 Caracas, height above the shores of the Bio Guayre, 2648 

 feet, inclination 42. 95. (Humboldt, Voy. aux Reg. Equi- 

 nox., t. i, p. 612.) 



Santa .6 de Bogota : elevation 8735 feet, inclination 

 27. 15 \ the chapel of Nuestra Senora de Guadalupe, built 

 upon the projecting edge of a rock, elevation 10,794 feet, in- 

 clination 26.80. 



Popayan : elevation 5825 feet, inclination 23. 25 ; moun- 

 tainous village of Purace on the declivity of the volcano, 

 elevation 8671 feet, inclination 21. 80 ; summit of the vol- 

 cano of Purace, elevation 14,548 feet, inclination 20. 30. 



Quito : elevation 9541, inclination 14. 85 ; San Antonio 

 de Lulumbamba, where the geographical equator intersects 



who, indeed, always reversed the poles, but who made his observations 

 with a needle which did not move freely, it follows that there has been 

 an increase in the inclination at the Cape of Good Hope of 3.08 in 

 89 years ! 



43 Arago, in the Annuaire du Bureau des Long, pour 1825, pp. 285 

 288. 



